I'm a college student who's a leader in my church's high school ministry. One girl recently revealed to me, while on a mission's trip, that she was abused by her parents, culminating in her being thrown out of the house at the age of 16. We talked and I assured her that God and everyone on the team loves her. Now that we're home, I see how much she struggles with her past and how hard she tries to hide what happened to her. She won't talk about it with me, and I strongly suspect that she's using drugs or alcohol to cope. How can I help this girl? God has really put it on my heart that I need to do something to get her off the path she is on.
Simply tell her that you had been thinking about what she had said and ask her if you might locate a safe home in which she might stay if she will permit. If she indicates she might be interested, talk to the older people in your congregation about housing. If possible, you will want to locate a couple who have experience in handling difficult teens.
Even if she turns your offer down, tell her you can see that she is under a lot of stress. The best cure for stress is good friends to talk about your cares and the worse would-be solution is using drugs or alcohol to mask the problems. Then let her know you are available to listen when she needs someone to talk to. When you do talk to her, make sure it is in public places. If you must meet privately always bring a woman with you. There is far too much temptation between a young man and a young woman when the young man feels he needs to rescue the young woman. "Brethren, if a man is overtaken in any trespass, you who are spiritual restore such a one in a spirit of gentleness, considering yourself lest you also be tempted" (Galatians 6:1). Don't ever compromise on this principle.
Beyond this, you can't do much yet because she has to be willing to accept your help. Please also keep in mind that you are only hearing one side of this story. If she is into drugs or alcohol, she won't often tell the truth about her situation. Always verify what you are told before acting on the information.