Julia Roberts was left devastated and anguished that she could not convince her half-sister Nancy Motes to enter rehab before her tragic drug overdose death in Los Angeles, Calif., on Feb. 9, Breaking Celebrity News has exclusively learned.

Motes, 37, a former production worker on the hit television show Glee, was found dead Sunday in a bathtub at a Los Angeles home, where authorities recovered both prescription and non-prescription drugs.

A source close to Oscar-nominee Roberts told Breaking Celebrity News: "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.”

As Breaking Celebrity News previously reported, Motes called the Pretty Woman star a “b*tch” and appeared to have called her a “hag” as she vented in a series of tweets sent late last month.

It was yet another illustration of the pair's rocky relationship after Motes previously declared Roberts led her to take the extreme measure of having gastric bypass surgery.

“When I was in high school and she was an adult, she would just let me know that I was definitely overweight,” Motes told the New York Daily News last year.

“She would make it quite clear to me and in a not-so-nice a manner.”

In tweets that have since been deleted, Motes wrote on Jan. 19 under the handle @Dabbs76, “So my ‘sister’ said that with all her friends & fans she doesn’t need anymore love. Just so you all know ‘America’s Sweetheart’ is a B—-H!!’”

She later added, “Do you want to be a fan of someone so cruel? She’s not even that good of an actress. Happy you totally F—ed with me?”