Mackenzie Phillips says she had sex with her dad. Did he ever have custody of her?

This is the most unfunny thing I’ve ever heard, yet when I read it, my first reaction was to giggle. Cause, I mean, it’s so off the wall and ridiculous and crazy, that what does one do upon hearing something so preposterously and incredulously grotesque? Save giggle? You know?
But apparently, One Day At a Time actress Mackenzie Phillips claims in her new tell all book, High on Arrival  “I woke up that night from a blackout to find myself having sex with my father. I don’t know how it started.” (Her father, for the record is former Mamas and Papas rocker John Phillips).
Apparently it (the having sex with dad situation) started around age 18 when she was strung out on drugs, and continued for a decade, consensually.
My big question is, did he and she ever have a custodial arrangement? I mean, as a child was he ever her custodial parent? Cause even at 18, I mean, child support continues till 21. So that is really….well, I’m not even sure why and if that matters. But I am just asking cause what does one ask in a situation like this? I’m stumped. Is she for real? Or is she still using drugs and thus her judgment/memory is impaired? Or what? OMG.
She’s going to be on Oprah reading an excerpt today, and unfortunately I”ll miss the whole thing since I keep forgetting to buy myself a television.