it does not matter if she eats the same amount as the other 2, if she's overweight she is eating to much, plus she does not exersize as much as the other 2, so she wont work it off like the other 2. the amount of food you feed should corrolate with the amount of exersize the dog has had BEFORE the meal. for example, if a dog has lots of exersize one day they should be fed enugh food to make up for what they lost, and if the dog gets veryt little exersize one day then that day the meal should be smaller.