Girl help, please?

I'm a girl and I've had a crush on this girl for a while now. I had the guys to tell her & we started getting close. Things were looking good but then she'd have these random mood swings or she'd get really upset over the littlest things. For example, if I were to use sarcasm, she'd get offended and not talk to me for days. She over reacts a lot. We started talking in February, it's now April and things are complicated. I guess she talks to her best friend about everything that happens between us & makes me seem like the bad guy. Her friend texted me (I didn't give her my number) and told me to leave the girl I like alone. I didn't wanna cause any problems so I tried to end everything. After I tried she said she was going to kill herself. So I couldn't end things. Which led to her best friend hating me more and threatening to fight me unless I leave her friend alone. I still really like her but she says she doesn't know if she likes me. I asked if she wanted me to get over her and again, she didn't know. I asked if she wanted me in her life, she said she didn't know. I don't know what to do honestly. I can't get over her, it's too hard. But all we ever do is fight, everyday. I don't wanna hurt her & she's honestly the only person I get into arguments with. I have no problem talking to anyone else and having a normal conversation but when it comes to her, it's just awkward because I'm afraid I'll say the wrong thing and she'll be mad again. Then she'll tell her friend and it'll tart more problems. What should I do? I definitely can't get over her. She refuses to talk to me in person, we've only talked once in person for like 2 minutes. They both can't look at me & we're all in one class together. I feel like if she'd let me talk to her in person then I could fix things. But that can't happen when the only time I see her, she's always with her best friend & she won't let me talk to her. I know she still likes me, I just think she doesn't want to because she knows I'm no good for her (or so her friend says) help me please!!!