Heather Graham
Man, I feel like an idiot. I watched this movie for the first time in a while, during the beginning when they're doing the experiment I thought to myself "Damn, that chick playing the mother's hot, kind of looks like Heather Graham," then I read the credits at the end. I also forgot she started acting in the late 1980s.
I went to school with a kid that claimed to be her distant cousin and told me all about the story when she was excluded by her family for making Boogie Nights. I guess he was telling the truth, if so what a small world.