somebody plz help me.

If あなた and your friend are fighting i suggest あなた sit her down and talk about it, find out how this got started and figure it out together.
However if she's threatening to beat あなた up and your frightened that she will do, あなた MUST tell your parents. Especially if your friend will actually hurt you.
But if she's just threatening あなた over the internet または on your phone, i wouldn't worry about it too much. Just block her number または change numbers on your phone and ignore her.
If あなた go to the same school try to stay away from her as much as possible. If あなた sat 次 to her in class go see your teachers before the lesson starts and explain to them what's going on and ask that they place あなた to sit somewhere else. This would also give あなた the advantage of getting to know someone else and probably becoming their friend.
If this friend of yours is leaving あなた alone at home, but bullying あなた at school, あなた MUST tell your headmaster/teacher または another adult who will then act accordingly. If things don't get better and あなた actually get hurt on school property によって this girl あなた can take legal action against the school for negligence.
If this girl keeps coming onto あなた at ホーム and school and no one is paying attention, i know this may sound drastic but i suggest あなた should go to the police and get a restraining order. However they will ask for proof that she's stalking and threatening you, so あなた must keep any record of what she says または does to you. If あなた get cuts and bruises from her photograph them, if she says something to あなた write it down in a notebook, keep text messages または emails, and if あなた can - tape any phone call she calls you.
But あなた should try sort it out with her. Sit her down and find out the root of the problem. あなた never know, if she turns up and あなた both listen to each other and talk about your feelings あなた could end up being best フレンズ for life :)
Good luck hun.

Is she on fanpop? If yeah, then レポート her. If not, tell your mom and dad XD

When あなた say あなた are fighting, あなた mean physically? Then あなた should tell your parents ASAP.

There's no need to be too worried. あなた started によって saying that she's your friend. So あなた either are または have been フレンズ before. あなた can easily make up with her if there is a true friendship in there. But if you're still worried, just make sure to lock your doors and windows just so あなた will feel safe.

What about threatening her? That usually works. または learn some moves, so that when you're fighting, あなた can kick her balls.