Sounds like a good first 2 up ride. There's very little movement for you to move with a passenger. Your hips hurt because she was clamping onto you. The helmets knocking together happens. If it's an experienced rider then they will know when they need to shift thier hand positioning (i.e. tank or waist). Trust me you do not want them leaning on you for extended periods. It'll piss you of on long rides.