"When she found out I was writing the book, she did everything to stop me," Mackenzie said. "I don't have history of mental illness, I have a history of addiction. I feel bad Michelle would do this. I think she is trying to protect the Mamas and Papas brand."
Chynna also defended Mackenzie against her mom.
"She doesn't have mental illness by the way," Chynna said about her sister. "I think my mom is angry... It's not something my mom wants plastered all over the papers."
On Wednesday, Mackenzie told Oprah Winfrey that she was first raped by her father in a hotel room when she was 18 while passed out after a drug binge but continued to use drugs and have consensual sex with him for years.
The relationship continued long after she married Jeff Sessler when she was 19, and ended only when she became pregnant and feared her father was the baby's father, Phillips said. John Phillips, she said, paid for an abortion.
Reading an excerpt from her new book, "High on Arrival," on Winfrey's show today, Phillips said of her first sexual experience with her father: "I woke up that night from a blackout to find myself having sex with my father. I don't know how it started."
"For a moment, I was in my body for a horrible truth," she said of waking up and realizing she had had sex with her father.
"I boxed it away. I started very early on in my life compartmentalizing. ... This was the mother of all difficult experiences. ... I [have spent] the last 30 years trying not to look at it," she said.
Mackenzie Phillips told Winfrey she confronted her father about the rape, but he characterized their relationship as romantic, Mackenzie said.
"After the first experience, I went to my father and said we need to talk about how you raped me. My dad said: 'Raped you? Don't you mean made love?' In that moment, I thought I'm really on my own here."
In 1980, soon after she'd been fired from "One Day at a Time" because of her out-of-control drug use, Phillips began to travel with her father's new band, the New Mamas and the Papas. It was during that time, she said, that she began regularly doing drugs and having sex with her father.
"It didn't happen every day, it didn't happen every week, but it certainly happened and happened many times," she said.
RUSSELL GOLDMAN, EILEEN MURPHY and LINDSAY GOLDWERT from ABC News contributed to this report