How about trying to work with your daughter, rather than getting into a power struggle? Why do you have a "no food or drinks in the bedroom" rule? Do you run short of dishes? Do you get ants? Does she share a room with a sibling who gets upset? We get ants, so we both try not to eat in bedrooms. Water bottles are okay, though, and so are sealed bags of things. I'm not into rules, but my daughter knows that if she eats in her bedroom, it's important to clean everything up as soon as possible so the ants don't invade. Because she understands the reason, she's pretty good about keeping dirty dishes and food remains picked up.
Sometimes she forgets, gets busy or whatever. If I happen to see a dish as I'm coming through or kissing her goodnight, I'll pick it up or ask if she can grab it on her way out. She does the same for me (I love a bowl of cheerios, walnuts, and chocolate chips when I read in bed). We're on the same side...
Single mom to Rain (1/93) , grad student, and world traveler