Roommate advice: BE PLEASANT AT ALL COSTS!! Roommates are not for a life time. In less than a year, she will be out of your hair (if you don't become friends in the mean time). The best thing to do it always be sweet and cheerful around her. If you allow her to get you down, you'll just have a miserable year. If you keep a smile on your face, you'll at least have a tolerable term.
I couldn't stand my first year roommate, so I made friends with a girl across the hall. Oddly enough, my first year roommate became my apartment-mate during my senior year, and we became great friends!
Good luck! Soon you'll have a whole bunch of life-long sisters
LM