My son isn't on any medications and he eats like someone is about to take the plate away - very fast and in great quantities. It was worse when he was younger. He had a weight problem from early on - he weighed 30 pounds at his one year checkup - because he ate so much. It's like he was insatiable. I think part of his eating was a compulsive thing because when he went to middle school he had the freedom to get what he wanted in the cafeteria and for a couple of months (until I realized what he was doing) he was getting 3-4 entrees and 4-5 desserts every day for lunch! He is obsessed with food for sure and is always concerned about what and when his next meal will be. In the past couple of years he has grown taller, learned how to control his portions and eat healthier foods, and has increased his physical activity, all of which have worked together to put him at a very healthy weight now. It's still all about food for him though.
The main things I can suggest for your daughter are lots of water (as someone else already said. Try squeezing lemon or orange in it if she resists) and an emphasis on healthy foods. Keep carrot sticks and celery cut up in the fridge and if she wants to munch, she can munch on those. High fiber foods may help her feel full longer, too. In my experience, trying to get my son to stop eating was never successful. He would resist, get defensive, get upset, and nothing would be solved. Keep her moving and keep healthy foods accessable. I think it would be good for her to have some control over her eating instead of locking all the cupboards and fridge. Maybe lock up some things but give her access to others?
_________________
You have wings...learn to use them and fly!