This girl has MAJOR problems with low self esteem. She gets obsessed REALLY easily and she just scares me with her low self esteem. She hits herself when she gets "bad grades" like 80s and makes a BIG deal out of little things like having a small quick convo she had with her mom about her report card (it was like any other report card talk anyone would get). Everything seems frigging HUGE to her, we live in new york so I guess thats a bit absurd to me. How do I help her be a bit more confident, shes been self pitying to the point where I am even tempted to slap her and scream at her to just accept reality. Ugh I'm such a lovely friend -_-

any advice?
well i dont slap her and stuff, and I've tried talking but shes just so stubborn, how do I sound non-preachy? and thanks I'll try being patient and more listening.

You can actually to talk to her first. A very decent conversation that does not sound too preachy nor psychiatist-y nor too your idea of a lovely friend who's slap and scream at her. She has major problems and as her friend, you should help her cope with that. After you've talked things over with her, you can do some action. Engage her in some extracurricular activities like performing on stage with groups. Let her meet your friends and let her hang out with groups. Support her all the way and little by little, give her some words of encouragement telling her that she's not alone. A lot of people can get not-so good grades and a lot of people can get into fights with their mothers and everything. It's not a good enough reason to just hit herself. Help her gain confidence and hopefully, she'll be strong enough to face these not-so big deal of a problem. You should also show her that you're confident. Rub them off at her. She needs you now so don't give up on her so she does not give up on herself. Both of you should be optimistic and with that, I wish you both the best of luck.