it actually does sound like a lot of food CC, can you cut down on the dry food, and monitor them all to make sure she doesn't pinch too much? It is very hard in a multi-cat household, but it isn't impossible to get them to lose weight - Tom lost 2.21, and I had 6 cats most of that 14 months, 3 overweight, 2 underweight and one that was fine. The girls were so happy when they could have their food down all the time again!! Think the others have covered a lot of it, is there anyway you can feed her somewhere she has to do more exercise? I used the top of the stairs for Tom, so he would go up and down my stairs a bit more!! And he had to work for his dry food, which I am now doing with Lucy too