Pardon me for being cynical. But there's one thing that puzzled me about the story. Firstly you say she was coached into going by friends, sure, not that unbelievable. But if she was coached into going there and truly unhappy there why wouldn't she tell you everything that happened? (Or your sister?) People who don't talk have something to hide. I know we all like to think that the people we know wouldn't do certain things, but young people are curious about drugs and sex, is it really that hard to imagine that she didn't want to go?
I'm glad that she's at the very least safe... and look, I don't know you, or your niece, but that's just my observation.