Have you discussed with her? You’d leave her hanging - and that might put her in a difficult situation.
You don’t know they’ll let you change - but I’d be honest. I just got to college and decided it should be a new experience. So I was a bit cautious and agreed to live with someone from High School but in retrospect, that will limit my growth.
They know kids in an undesirable dorm want to move - I don’t think you need to mention the why a certain dorm. Just request it.
But you should be upfront with your roommate that you are trying to move on from. You did agree to room with her and that should mean something.
Good luck.