It's pretty terrifying for a lot of people, I think, to realize how little food a spayed, indoor, small dog needs to eat. You can round things out by mixing green beans into her food to bulk it up. If she turns up her nose at them, cut her food back and leave some on the kitchen floor (or in her crate if she uses one) and you will probably find that after a few days she will come around. You could also soak/cook them in some salt free/fat free chicken broth to get her to try them. Once you have something to fill out her bowl with, you'll feel better about it and so will she as she trims down.