Sorry you are going through this. I agree with the others that you try to talk to parents about it again. That may not work though. I think people don't take siblings fighting seriously enough.

My younger sister was violent and my mother was pretty much a mentally absentee parent. The only way I managed was to not have any interaction with her at all when she was angry. Even if I had to go outside and climb up a tree. She came after me there once but discovered that it was difficult to have a fist fight in a tree.

Her violence was never addressed when she was a child and now she's a violent adult.

The only thing I can tell you is to try to be aware when things are escalating towards her attacking you is to get away from her. When she's in a rage there is no point in trying to talk to her.

It does sound like she needs therapy.