LOS ANGELES, Calif. --

There has been plenty of fallout from Mackenzie Phillips’ shocking revelations last week that she had a decade-long sexual relationship with her father. And for the first time, her “Celebrity Rehab” roommate, Mindy McCready, opens up to Access Hollywood’s Shaun Robinson, revealing what Mackenzie told her about the “One Day At A Time” star’s dark family secret.

“Did she ever tell you about what happened with her father?” Shaun asked in Access’ exclusive interview with the country star, who will appear on the next installment of VH1’s “Celebrity Rehab,” which begins airing in January 2010.

“During the taping she so kindly and graciously let me read the book. I was the only one that read it,” Mindy said. “Just knowing her, how I knew her from the show, it was really touching. The book? Just woah!”

Never doubting Mackenzie’s shocking confession that she had a 10-year sexual relationship with her father, John Phillips, an emotional Mindy revealed that while taping VH1’s “Celebrity Rehab” in June, a Phillips family feud was already brewing.

“During ‘Celebrity Rehab,’ the family was finding out that she was going to discuss these things and of course, you know, no one wanted her to discuss them,” Mindy said.

The Phillips family is split on whether to believe Mackenzie. Half-sister Chynna does while Mackenzie’s former stepmother, Michelle Phillips, does not.

And unleashing stinging words of contempt on Twitter, Mackenzie’s other half-sister, Bijou Phillips, wrote, “When I was young my sister told me about this, It ruined my life and my relationship with my father.”

She added, “Exploiting the history of our family and the death of our father John Phillips for the release of a book is disgusting.”

On Tuesday afternoon, Bijou’s Twitter account had been deleted and the posts removed.

But Mindy stands up for Mackenzie’s right to speak out.

“Nobody has the right to say what they do or don’t believe,” Mindy told Shaun. “Dealing with a 30-year long drug addiction problem doesn’t just encompass the drug, ‘cause there’s a reason why she went to that in the first place.”

“Since the book came out, has she said to you that she regrets going public, because she’s been under so much scrutiny?” Shaun asked.

“No, she has not said that and she better not say that. In order for you to be better you have to get real with yourself and with your friends and family members. No matter how hard it is and no matter how difficult the subject matter the truth has to come out,” Mindy said.

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