I'd like to state that if you're feeling suicidal, that you should call the suicide hotline [1-800-SUICIDE (1-800-784-2433)], or find professional help. If you cannot find any professional help, tell your parents, a close friend(s), a close family member, or the school counselor. I'm sure they'd be more than willing to help you with anything. Also, don't do anything that you might regret. Try to think through everything as logically as you can.
As for this girl, have you tried working it out? Perhaps she just needs some time to get over things, or she's just having a rough time and this is just her way of dealing with things. If anything, just try talking to her, apologizing (if necessary), and ask her what you can do to make everything better between you two. If, in the end, it does not work, remember that unrequited love always goes away with time. Again, as stated before, don't do anything harmful to yourself.
If you still feel the need to talk, you can always PM me.