Chance gained about 1/2 lb. after being neutered, but I haven't changed his feeding schedule. Spaying and neutering changes their metabolism even if your Vet tries to tell you it doesn't. The weight gain may very well not be from over eating.
Just keep her active, and she should be fine. If you feel like she is packing on to many lbs., you can change to a weight management food and that should help with calories, and fat.