I'm betting this has happened to her before. You could just be honest with her and tell her, I'm sorry but this isn't working out for me. I'm not having fun. If she offers to change or asks for a second chance, you could say you could try, but if it gets heated as you say, you could just repeat, this isnt working out for me (or something similar - whatever works for you). I wonder if no one has ever confronted her with her behavior before. Anyway good luck.