I am sorry this happened to your friend and that she is going through a hard time because of it. The best thing for you to do is tell her you care about her and that you are concerned about her behavior. I would recommend that you suggest your friend get professional help to assist her through this. However, unfortunately if she won't help herself there isn't much you can do. Here is an article about how to support rape survivors that you might find helpful:
http://pandys.org/forums/index.php?showtopic=49460 If her drug use gets out of hand and you are afraid for her safety the best thing you can do for her is notify her parents. I hope things turn out okay. Good luck with everything. Feel free to
PM me anytime you wan to talk.
<3 Mimi