You have to keep reporting. Schools often ignore bullying complaints because they have certain policies they have to follow. But the more you report and cause an uproar with staff (don't go ballistic but keep going higher and higher) they will have to do something. Even if it means going to the head of the school, or even higher. Its definitely scary, I completely sympathise with that. But the longer you leave it the worse it will get. You deserve to feel safe when you go to school.
You can try restraining her if she hurts you, but because you're a guy she does have a card to pull. And schools are very finicky about restraining and gender disparities when it comes to bullying.
It will be harder for you because you're a guy and she's a girl, people don't think it's possible. But the best thing you can do is not retaliate and get yourself into trouble as a result.