Have you been to see a doctor to rule out any medical problems? Otherwise, is she overweight? If she is, you might want to see your doctor about it. If she isn't, what about just giving her more to eat and drink at meals until she is satisfied, rather than trying to stop her. I really don't think it's a problem to give her as much water as she wants to drink, as long as it's not ridiculous amounts at once (eg more than 2 cups at one go). It sounds like she is reacting to you trying to control her food and drink intake, so if you don't make it a battle then her constant obsession with food might stop.