Julia Roberts isolated Nancy Motes from their mother, according to a friend.
The Oscar winning actress changed Betty Lou Motes' mobile phone number and the locks to her house in order to cut off her half-sister - who took her own life last Sunday (09.02.14) - after she gave a tell-all interview, according to Nancy's close friend, Jerem Hutcheson.
Jerem told the New York Daily News newspaper: "Nancy was very close with her mom, and when they changed the locks and [later] relocated her, it was devastating to Nancy.
"She couldn't reach her mom when she needed her most.
"I think [Julia] was resentful of the relationship Nancy shared with their mom and also did it out of spite."
In Nancy's interview she told how Julia had teased her about her weight when they were younger and said they were "both trying to change our opinions of each other".
Nancy also reportedly left a "ranting" suicide note in which she is rumoured to have said Julia "drove her" to suicide.
Nancy died of an apparent overdose of prescription medicines, but Jerem denies she was a drug abuser.
He added: "Nancy didn't have a drug problem. She had an overly emotional moment and acted on it."
Nancy was engaged to fiancé John Dilbeck and they were planning their wedding at the time of her death.