well since you have tried getting through to her yourself and it was unsuccesful... you may want to go to a teacher that you trust of a principal or vice principal or like a guidance counsellour they can approach your friend and she will probably talk to them more easily because she wont have fear of being judged that is the best way for you to help out without her getting offended or upset or anything of that nature but you should step in soon because it sounds like things arent getting any better any sooner