What do I do? Friend help? Please?

Your dealing with a bully. She is obviously targeting you because she's insecure with herself and she chose you as an easy target. Anyway, I have had troubles with people like that in the past, and I tried multiple ways, but the best way was going to the principle and telling them about your situation. Nobody will think your a rat or a wimp and it will soon be forgotton. The principle will most likely keep an "eye" on her or ask a teacher too, then when she does something, a teacher would see it and she would get in trouble for it. She will stop after that.