Well, what did you do with the kid? How did she respond?
The food thing is likely her testing her independance of you. Reinforce the WHY of the no food rule. Maybe rent a carpet cleaner and let her spend a Saturday helping to clean the carpets. That autta send a pretty clear message
Or, show her the pictures of the glue traps (that are in the close ups thread I think) with all the bugs on them, and tell her that's what will be colonizing her bedroom if she doesn't keep the food out of there. Good luck.