Where does her obsession of turning off lights come from?

Lights out: It could stem from many things. Perhaps it is compulsive behavior as seen in ocd. Perhaps she is a conservationist and prefers not to waste electricity. Perhaps she is on a tight budget and doesnt want to waste money. Perhaps she gets migraines and the light botbers her. Maybe you should ask why are you so bothered by her turning off the lights...Just saying.