My best friend moved schools and now she is a mess?

ok so we were best friends. and then she moved to a private school. She was upset but then she meta boy. She says she's in love with him. she is only 13. a while ago she told me she's had with him twice. i was completely shocked, ive known her for years, and i can tell she deffinatly wasnt lying. By the sound of it, he really messes her about, like one minute he says he loves her the next he breaks up with her. And she just begs for him 2 come back. And shes been slitting her wrists lately. my other best friend read her texts (i no its a horrible thing for her to do and i did get really mad at her for it). but apparently her boyfriend text her saying. i dont no if i can do this anymore, it wont stop bleeding, it really hurts. What's going on? how do you think i can help, withot actually brining it up? i no she would start avoiiding me if i brought it up, so what do i do?