Her late father had an incestuous sexual relationship with her and possibly raped her. She also may have aborted his love child as a young woman.
But Mackenzie Phillips' affair with John Phillips was not, she says, as simple as all the news headlines make it seem. Nor was it necessarily as bad.
Her father was not a monster, and that 10-year “affair” Mackenzie is said to have had with him is not easily categorized, the troubled star told Oprah.
“My father was not a bad man. He was a very sick man,” she said.
"If anyone out there can possibly separate [John Phillips'] body of work from his personal demons, I think that would be the honorable thing to do."
Mackenzie Phillips, 49, added that her father - with whom she says she also did drugs - "didn't set out to hurt me. He did the best with what he had."
She also reports that their relationship - which she details in her new book, High on Arrival - lasted 10 years until she ended it when she got pregnant.
A pregnancy that ended with her aborting her father's love child.
"To call it a 10-year relationship is not correct," she said in another interview on Today. "It was a warped event, that occurred over time. At 18, I was molested. Maybe three years later, I started waking up with my pants around my ankles."
She told Oprah Winfrey that she had an abortion, which her father paid for, "and I never let him touch me again" after dealing with the ramifications of that.
Though she says she does not blame herself for her the incest, Mackenzie Phillips says, "I believe I have some accountability for what went down after."
Some of her family is standing by her, including Mackenzie's half-sister Chynna Phillips, who says she first heard about this 11 years after it ended.
But her step-mother Michelle Phillips isn't buying it, telling ET:
"Mackenzie's drug addiction for 35 years has been the result of many unpleasant experiences. Whether her relationship with her father is delusional or not, it is an unfortunate circumstance and very hurtful for our entire family."
Despite the criticism from her stepmom, Mackenzie said on Today that "the outpouring of support from other incest survivors has been phenomenal."
"This is a subject that is so incredibly taboo, as it should be, but there needs to be a dialogue about it," she continued. "The covers need to be pulled."
Follow the jump for a video of Mackenzie Phillips on Today ...