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As for your friend... It's terrible that she's going through this, and that it puts so much pressure on you. I'm sorry you're both struggling with this. But the best thing to do is to just be there for her. If you think it's bad enough, tell her parents if they don't already know. and even if they do know it might help to tell them that you think she's getting worse. If you're worried that she'll hate you for it, i totally understand (i have been in a very similar situation). But remember that her safety is more important. She will probably actually be glad you stepped in in the long run. Just keep being strong for her.
I hope that helped at least a little. good luck! and i hope to see you around!