You could always put your iPhone inside something. You only need a small hole for the camera to view through. If her room or the bathroom is cluttered or has lots of stuff in it may be easier to find a place to hide it. Only an idea hope it helps. Always risks involved.
至 Mymom998 :hide in plain sight, with an app which has your phone secretly recording. leave it in your pants pocket, camera poking out, and pretend you just forgot your jacket there?