Hello, I'm new to the forum too and don't really have any answers. I just thought I would post a reply to let you know that you're not alone. This girl sounds dreadful and I can't understand what would make a person behave that way towards you, especially since you didn't reject her. I think it will blow over, you just need to try to stay strong in the meantime. Don't try to speak to her and concentrate on yourself.
Hugs,
Shelley