(at least in cali), the 3rd brake light will probably be an issue. at the dmv here, they check to make sure you headlights/tailights/brakelights work. i don't think they check the tires, or care about the seatbelt.

and (again, at least for cali) she doesn't need to be on your insurance policy. how would a person without a drivers license get on an insurance policy anyway?