The paranoid part perhaps means something related to peeping/vouyerism happened to her or someone close to her. See if she's willing to talk about why she covers the phone cameras. Perhaps she suspects the light has hidden camera? Would that light be the type where hidden camera can be installed instead of just simple light?

There's two things you can do. First is to find out what is the trigger for the change. It won't be easy to do this. Second, is to get matte film and cover up all reflective surfaces, change the light's fixing to matte, and such. Reduce any reflective surfaces you can. Use a phone case that cover's the camera. Simple things to help her 'calm down' a bit. Maybe then she will start talking. Sometimes you have to go extra length to be her perceived 'ally'.