Bro, You need to get her to chill. Tell her that you don't love her that way. Also follow @Sample_Text's advice

Breaking her 'heart'

is probably the only option you have

or you could give her your attention i'm pretty sure that's all she wants from you .
she's just using some crazy ways to get it

restaining order -_- maybe

You may actually be the one who can stop it. See, if she likes you, she is more likely to listen to you than someone she doesn't care about. You can ask to talk and she'll take time to listen to you more than she'd even listen to a teacher. Explain to her that you've seen her bully and hurt people just for liking you and it makes you feel bad, not just for them, but for yourself. You could tell her that it's like you're partially responsible because she does it because they like you, and you need her to stop. Anyone can get jealous and can do things that end up hurting others, but liking others is actually a good thing. Encourage her to try to see that, when everyone gets along, their happiness spreads, but when people don't get along, their misery spreads. I'm pretty sure those people who were hurt by her don't like her now, so it's best for everyone, even her, if people get along. You can explain it any way you want, but it may only be you she listens to. You can stop it. :)

Also, even though you may not like her, she may need a friend. Acting out so violently can be a sign that she has some problems with emotional control and needs someone to support her so she doesn't lash out. You don't need to hurt her feelings, just give her an alternative. Sometimes the thing people most want is the one thing they can't have, so giving her friendship may be a compromise that eventually makes her less obsessed because she sort of partially has you without the rejection. That's an option anyway.

I'm not sure if you've heard of "Yandere Simulator" but your story reminded me of the game. She wants you to notice you, thats all. Probably should try talking to her, maybe say stuff like "If you really care about me than can you please stop hurting other people?" Or something like that.

Talk to her about this, but dont hurt her, be gentle, girls like this who are insecure and possibly emotionaly unstable, can lash out very harshly. But dont let her guilt trip you, or push you, be stern, but not meen.
Tell her that, you are flattered by her liking you, but you do not feel the same. There is someone out there for her, but its not you. she will move on from you, you just need to cut the cord, quickly, but carefully.

I hope this helps, being a girl myself I know she is probably insecure, and could possibly be neglected at home, or spoild.

If you want, you can tell her you can still be friends, as long as she stops hurting people.