I feel extremely sorry for you gf to have to go through this....

I have a 14 to daughter, who thank god is good kid. She does however have a friend who is going off the rails, due to circumstances at home, she has it pretty tough and I feel sorry for her, however, she trys to drag other kids including my daughter with her. I'm wondering whether your gf's daughter may have a friend like this... Peer pressure can be very hard to withstand and if a child is not as self confident or is easily led it can be very hard for them to say no, especially if they want to be in the "Cool" group.

My daughter has pretty much severed her ties with the girl in her school, guess I'm very lucky that she has a strong personality.

I hope everything works out for you gf before things get beyond control.