Appearing on the Oprah Winfrey show, she said that she and the King of Pop were 'really in love' but that she ended it because of his drug use.
She explained: 'I had to make a decision to walk because I saw the drugs and the doctors coming in, and they scared me. They put me right back into what I went through with my father. That ended it.'
The 42-year-old, who married Jacko in 1994 and divorced him two years later, said that she wished she had done more to help the troubled star.
'I know it's naive to think that I could've, but I wanted to,' she explained. 'Had I just said, 'How are you?' Can I try to make a phone call? I really... regret that I didn't.
'I think that was a train heading in a certain direction that no one could have stopped. I've had to really get my head around that in order to stop the pain.'
Recalling her 2005 last 'coherent' conversation with the star, who died from an prescription drug overdose last year, she added: 'I was very distanced. He was trying to throw a line out to see if I would bite emotionally, and I wouldn't.'
He asked her if she loved him, to which she replied: 'I told him I was indifferent. He didn't like that word. He cried.'