Is it against the law to put a padlock on your fridge and pantry when there are children in the house?

I recently got custody of my three teenage children. Where they were living before, they had to hide to eat because they were being starved. I cook 3 meals a day..and give 2 snacks. My daughter eats constantly. I have tried to control it because she has gained 20 pounds in the past 3 weeks. She has now started sneaking food. The worst part is that she wastes a lot of the food she sneaks. I have a $400 budget per month for food, and I cant afford to continue like this. I was told that it is considered child abuse to lock up my pantry and my fridge. Is that true? If I can't lock it up, I wont have enough food to get through the month. If it is against the law, can anyone give me suggestions? I have an appointment scheduled for counseling, but they can't see her till the end of July.