Try charcoal biscuits. Alot of times, the smell is just coming from the stomach. Charcoal absorbs the acids and the smell. You can also try parsley. It works really great! Darford sells biscuits that contain charcoal, peppermint, parsley, and chlorophyll, which are all great for the breath. You can get them at pretty much any pet supply store or Wal-mart. My friend's dog has a sensitive belly and she does fine with these.

Raw bones are great too. They clean the teeth SO well. Have you tried these to see if they are okay for her tummy?