Julia Roberts tried to get her half-sister to go to rehab in the months before her death.
The 'August: Osage County' actress had a "complex" relationship with Nancy Motes - who was found dead in a bathtub from an apparent drugs overdose on Sunday (09.02.14) - that was reportedly made worse by the former production worker's addiction, and Nancy's public attacks on her famous relative were often triggered by the actress' pleas for her to seek help.
A source told RadarOnline.com: "The sisters had a very complex relationship. They used to be very close when they were younger. Julia tried in vain over the years, even in the last six months, to get Nancy to go to rehab. Nancy refused the offers and that is when she would often publicly lash out at Julia.
"It hurt Julia, but she knew her sister was battling addiction.
"The addiction to prescription drugs made Nancy a totally different person. There would be periods of sobriety and with that brought clarity. It would be during those moments that the sisters would reconnect. Sadly, of course, those times became less frequent before her death."
The 46-year-old actress arranged for Nancy - the daughter of Julia's mother, Betty Lou, and stepfather, Michael Motes - to check into rehab last year, but she "backed out" shortly before she was due to enter the facility.
The source added: "She had agreed to go... this was about a year ago.
"At the last minute, Nancy backed out, gave no reason. Yet, Julia told Nancy if she was ready to get healthy, all she had to do was call. Julia never got that call.
"Julia is taking the death very hard. It's extremely difficult for her because it didn't have to happen. Julia has a great support network around her and she is relying on her husband [Danny Moder], more now than ever."
It has been reported that Nancy left a "ranting" suicide note in which she blamed Julia for her problems.

Kylie Minogue "cried" the first time she heard her duet with Enrique Iglesias.
The 'All the Lovers' singer has teamed up with the 'Hero' hitmaker on ballad 'Beautiful' and she says it was an "honour" to work with him.
She said: "From my new album, 'Kiss Me Once,' this is the one and only true ballad. It's a duet with Enrique Iglesias and it's an honour singing with him. I actually cried the first time I heard it and I knew I had to be part of this incredible, romantic and touching song."
The 45-year-old singer is also a big fan of Marvin Gaye's 'Sexual Healing', which she thinks is the "ultimate sexy song".
Discussing her Valentine's Day playlist, she said: "What words can be added to this, the ultimate sexy song? Its magic never diminishes and it is still as hot as ever!"
When she's at home alone, Kylie enjoys singing other people's songs and is happy to give her private performances her all.
Continuing other songs on her Valentine's playlist, she said of Minnie Riperton's 'Lovin' You': "Everyone get ready....who will hit those high notes? Love this song and no-one does it like Minnie."
And of Bonnie Tyler's 'Total Eclipse of the Heart', she added: "The ultimate power ballad. I love singing along to this and always, always include the 'air grab'."
To pre-order Kylie Minogue's new album 'Kiss Me Once,' please visit www.itunes.com/kylieminogue

Britain's Prince William has urged the world to come together and put a stop to illegal wildlife trafficking.
The 31-year-old royal arrived at London's Zoological Society this morning (12.02.14) and appealed from everyone to help save endangered species such as rhinos, tigers and elephants.
He said: "The forces destroying some of the world's endangered species are sophisticated and powerful.
"But this week we are seeing the creation of an equally powerful alliance coming together to help fight them.
"The commitments set out today will begin to address the challenges of protection, enforcement and demand reduction. We will use our combined resources to ensure they succeed.
"But ours is not an exclusive partnership. It is my hope that you will all become part of United for Wildlife and the global alliance to stop illegal wildlife trafficking."
The prince will also deliver a more in-depth speech tonight at the Natural History Museum in London to the heads of government, ministers and experts on the subject from around the world.
However, a few days before the start of the anti-poaching campaign, William and his brother Prince Harry reportedly went hunting for a wild boar in Spain.

DJ Fresh refused to do a collaboration with Alexandra Burke.
The 36-year-old producer admits he snubbed the 'Bad Boys' hitmaker - who shot to fame after winning 'The X Factor' in 2008 - after she chased him around a dressing room asking for a duet.
Speaking to Hits Radio presenter Darryl Morris, he said: "One of the massive 'X Factor' people was chasing me around these dressing rooms.
"[She was] leaving notes for me everywhere saying they wanted to work with me and then kind of got up in my face and gave me their phone number and was like, 'make sure you call me, make sure you call me' and I was already thinking, that you're a good singer and stuff, but you just wouldn't fit on my music and I already knew that I wasn't going to be calling her.
"It was really awkward... She's very sweet and it's just awkward because you can't really explain it to somebody. You don't want to be offensive but it's kind of like you just wouldn't fit on what I do."
Meanwhile, the 'Dibby Dibby Sound' hitmaker recently announced Ellie Goulding would be featuring on his new single 'Flashlight' later in the year.

The Vamps have announced their first ever UK tour.
The 'Wild Heart' hitmakers took to Twitter this morning (12.02.14) to thank their fans for their constant support, and have confirmed they will hit the road later this year to perform in 11 different cities across the country.
They wrote: "The time together we've had has been totally amazing- you guys have been great and we won't forget these incredible memories...
"Even from the start, you have supported us relentlessly and we owe so much to you. These times have been life changing for us...
"We have met some amazing people along the way. With all that said, we have been forced to make this decision. We regret to announce that...
"...We can't meet more of you on our DEBUT UK HEADLINE TOUR AHHHHHHH!!! We LOVE YOU AND CAN'T WAIT!!! LET'S HUG (KISS) (sic)."
Meanwhile, the boyband - consisting of Will Simpson, Connor Ball, James McVey and Tristan Evans - have just wrapped up their supporting slot on Taylor Swift's London gigs during her Red tour.

The full dates of The Vamps' UK tour are as follows:

Sheffield City Hall - 23 September, 2014
Newcastle City Hall - 25 September, 2014
Glasgow SECC Clyde Auditorium - 27 September, 2014
Glasgow SECC Clyde Auditorium - 28 September, 2014
Manchester O2 Apollo - 1 October, 2014
Manchester O2 Apollo - 2 October, 2014
Liverpool Echo Arena - 4 October, 2014
Birmingham NIA - 5 October, 2014
Brighton Centre - 8 October, 2014
Cheltenham Centre - 9 October, 2014
Cardiff Motorpoint Arena - 11 October, 2014
Bournemouth BIC - 12 October, 2014
London Eventim Apollo - 14 October, 2014
London Eventim Apollo - 15 October, 2014

Ant and Dec couldn't "bear" filling in for Simon Cowell on 'Britain's Got Talent'.
The presenting double act stepped in for the talent competition's head judge when he was off sick during this year's auditions, but they admit they struggled to be critical of the acts on stage even if they weren't good.
Dec said: "We had a day where we filled in for Simon when he was ill. I say a day, but we did a couple acts each and after that we had to make our excuses and leave. We couldn't bear it.
"We weren't mean, but we were trying our best to be!
"As soon as you hit the buzzer, they look at you and you go, 'I'm so sorry, I didn't mean that, the other judges made me do it. You're very talented, you can go through. You've won!' "
Ant, meanwhile, says he and Dec were very apologetic to acts that they weren't impressed with.
Speaking to BANG Showbiz at the London auditions yesterday (11.02.14), he said: "They deserved a buzz but even though they deserved it, it was very hard to press that buzzer. And yeah, we apologised to them afterwards."
The latest series of 'BGT' will see the show's hosts given some power as they - along with the judges - will be able to press the new Golden Buzzer, which sends the act on stage right through to the live semi-finals. However, they can only exercise this special privilege once.
Dec explained: "I'm sure the time will come, if there's an act we really love and the judges don't, we might be tempted to run down and hit it. We've certainly got that in our back pocket."

Simon Cowell has branded Girl Thing "bitter" following their appearance on 'The Big Reunion'.
The 'X Factor' mogul addressed criticism from his short-lived girl group - who were dropped by their record label after releasing just two songs - and thinks their comeback on the ITV2 show is ill-advised.
Quizzed if they will be more successful this time thanks to 'The Big Reunion', he said: "No! I wouldn't do it."
Simon, 54, also weighed in on band member Linzi Martin's claims she wrote the verses of hit song 'Pure and Simple', which was later a UK number one single for reality TV band Hear'Say.
Speaking to BANG Showbiz at the latest round of 'Britain's Got Talent' auditions in London yesterday (11.02.14), he said: "What happened was, the guy that was managing them, I got him the gig to manage 'Popstars' [winners], Hear'Say. He gave my song, 'Pure and Simple', to Hear'Say. It was my hit record.
"That's why we didn't do what we hoped we were going to do with that group. It's as simple as that."
He then added: "All failed groups are bitter."
Girl Thing - also consisting of Jodi Albert, Anika Bostelaar, Michelle Barber and Nikki Stuart - were tipped as the next big thing in music when they released their debut single 'Last One Standing', but the group failed to make an impact on the charts.

ITV are launching a new channel.
ITVBe will offer UK and US lifestyle and reality shows and be the new home of 'The Only Way Is Essex' and the 'Real Housewives' franchise - which both currently broadcast on ITV2 - when it launches later this year on all major broadcasting platforms, including Freeview, Sky and Virgin Media.
Adam Crozier, Chief Executive of ITV, said:"ITVBe will be a terrific new addition to our family of channels. It reinforces our plan to maximise audiences and revenues from our broadcasting business. Alongside our recently-announced new pay channel ITV Encore, this is another important step forward in our strategy to become the most watched, most loved and most talked about family of free and pay channels for every household and every advertiser in the UK."
The new channel will mainly be targeted towards a female audience and is seen as a sister channel to ITV2.
Peter Fincham, Director of Television at ITV, said: "Expanding ITV's family of channels to introduce a new free-to-air, female skewing channel focusing on entertainment and reality means our viewers will have access to even more great content. We identified an opportunity to develop what is currently part of the ITV2 schedule - reality and non-scripted shows, which are very popular with young women and housewives with kids - into a distinct channel proposition, aimed more squarely at that audience.
"ITV2 will continue to be the youngest channel in our portfolio, outside of CITV, and the strategy of bringing more scripted series, both acquired and commissioned, will continue apace, alongside panel shows, formats and other young skewing commissions."

January Jones has been cast in horror flick 'The Shuddering'. The 'Mad Men' actress will play the lead in George Ratliff's supernatural thriller, according to The Hollywood Reporter. The script was penned by 'The Haunting in Connecticut 2: Ghosts of ...

Michiel Huisman will star alongside Blake Lively in 'The Age of Adaline'.
The 'World War Z' actor has been cast as the 'Gossip Girl' star's love interest Ellis in the romantic drama helmed by Lee Toland Krieger, who is delighted to have him on board.
The American filmmaker said: "Michiel Huisman is the rare breed of actor who radiates charm and sophistication while possessing a unique, enigmatic kind of vulnerability. He's the perfect addition as Ellis, and I couldn't be more excited to have him join our cast."
The supernatural romance tale is a co-production between Sidney Kimmel Entertainment and Lakeshore Entertainment with Sidney Kimmel, Tom Rosenberg and Gary Lucchesi attached as producers.
Jim Tauber and Eric Reid executive producing for the film which is expected to begin filming in March.
The script was written by Mills Goodloe and Salvador Paskowitz, with revisions by Allison Burnett.
The long-stalled movie - which was first planned in 2010 - recounts the life of the 29-year old titular character Adaline (Lively), who stops aging after recovering from a near-fatal accident.
After years of leading a solitary life and travelling across the globe, she meets a man for whom it might be worth losing her immortality.
'The Age of Adaline' is set for an all-star cast which includes Harrison Ford and Ellen Burstyn.

Babyface is engaged to his long-term girlfriend.
The record producer confirmed that he has popped the question to former dancer Nicole Patenberg after seven years together.
The star - real name Kenneth Edmonds - told The Los Angeles Times newspaper: "I'm happy to say I'm on the love marriage path. I'm a very lucky guy!"
The 54-year-old star - who has five-year-old daughter Peyton Nicole with his fiancee - insists honesty is the key to a happy relationship and thinks couples should deal with their problems head-on.
During an interview with BET, where he was discussing a collaboration between himself and Toni Braxton on their new record 'Love Marriage & Divorce', Babyface added: "The main thing is being honest with yourself and being honest with your feelings. When we're not honest with ourselves, we just accept situations, don't talk about them and, as you said, ignore the elephant in the room.
"You better recognise there is an elephant in the room and deal with it, because a lot of times the elephant in the room is the one that you put in there, so you have to deal with it."
Babyface split from ex-wife Tracey Edmonds in 2005 after 13 years of marriage and put their split down to irreconcilable differences. The pair have sons Brandon and Dylan Michael together.

Sarah Silverman is dating Michael Sheen.
The comedienne was reportedly seen "making out" with the 'Frost/Nixon' actor at Hollywood nightspot Soho House last Thursday (06.02.14), and insiders have confirmed they are now a couple.
A source told Us Weekly magazine: "They were making out at Soho House. They were all over each other for a lot of the night."
The pair also seemed close at Michael's 45th birthday celebrations at Craig's last week, where they joined revellers including his 'Masters of Sex' co-star Lizzy Caplan, Nicole Richie, Kate Hudson, Demi Moore and his former partner Kate Beckinsale and her husband Len Wiseman.
A source said: "Sarah and Michael came and left together. She drove. When they left, Sarah opened her trunk so Michael could put all of his gifts in and then they drove away."
Michael - who has 14-year-old daughter Lily with Kate - briefly dated VH1 presenter Carrie Keagan last year and was in a relationship with his 'Midnight in Paris' co-star Rachel McAdams for two years until February 2013.
Sarah was previously in a relationship with Jimmy Kimmel, but they split in 2009 after five years together.