I think the best way to help her is to befriend her and invite her to do things with you. At least that way you know that she isnt going to be doing something else that is haraam. If she is surrounded by loving supportive people, it really helps alot.
Do you have any family, eg. parental role models for her that could also help? Maybe she just needs the love of a father figure or someone else that treats her like she wanted to be treated?
Sometimes, its easier to do the wrong thing to compensate for the void in ones life. Support her, talk to her and hopefully she will maybe start to reveal what she wants in life.
the dark past is coming and hunting her, let her do what she wanna do for a while, in the meantime be in contact with her all the time. Slowly and steady .. try to take her away from current habits.
Gr8 Mashwara.