We just bought a new bed for my son. He started out wanting a double, ended up with a twin when we went shopping. In the end, floor space in his smallish room won out. (His choice) And he got a cool bed (it has storage underneath and a bookshelf along the side. While there isn't a lot of room for a teen to spread out in a twin, dorm beds aren't any bigger if you are planning on sending them off to college.
I'd lay out a sheet on the floor of the room (or string) and get a good idea of how much room a larger bed will take up. If the room fits it - and you still have room for a dresser or whatever else she wants in the room, a full is very nice. Both my kids have smallish rooms, while they will fit fulls, things would be tight.