Having raised 6 girls myself, 2 of them who quite clearly knew far more than me at 16 years old (I know this because they proudly told me how smart they were) and also who both moved out at that age to live with "a friend" mostly because they hated the rules at home (take out the trash, clean your room, you know, the real awful stuff) but also because they wanted to do stuff they knew full well I'd never approve of... this kind of behavior isn't surprising at all.
It's a complicated age. You can't just lock them in the house, and when they do leave, there's almost nothing you can do about it, but HOPE they stay in touch and are safe and that no one takes advantage of them in any way. I definitely understand what her parents are dealing with right now and why they have no interest in speaking to the media.