Have you considered a raw diet? Nature's Variety, Primal and some other great brands exist that prepackage raw meals and often this aids in smelly breath. If its coming from her stomach, the best thing to do is get her on a whole food/ raw diet.
Ditto on everyone else's thoughts on retained milk teeth. My baby girl had retained many teeth and she had the most rancid breath, even on the raw diet. Now, three weeks after her spay/ teeth surgery, she finally has the lovely puppy breath everyone keeps mentioning.
