Omg that would be awlful.....
Is the seat still backward or facing forward? I would turn it around faceward and see if that helpsshe can see out the same direction as the car is going..... Put the normal radio/music on up loud to drown her out ..... Ykwim .
Oh and if you have your car windows down don't forget that revolting noise one window can make could be aggrevating and hurting her ears hense the crying ..... But really apart from trying to ignore her I haven't a clue sorry.