Did she do something to hurt you? If she committed an inexcusable offense, then I think it's normal to hate her. However, she is "innocent" then it could be due to one of your disorders. Where are you with your bipolar? Mania can make you really irritable and irrational. However, it is also a classic BPD thing to idealize someone and then hate them.

Regardless, I think you should forgive her just so you can have some peace.