While she's losing her baby teeth the breath can be simply rancid. The upside is that it won't last forever. Once the baby teeth are all gone her breath should improve. Depending on her age you may want to consider taking her into the vet and letting him remove the remaining baby teeth.
Tooth paste for dogs is best to use, you can get it in flavors she will like and use a soft baby tooth brush. You can also get a brush that will slip over your finger.
If you're feeding a moist food you may want to consider a dry kibble, at least until all of the baby teeth have worked themselves out. Premium diet and regular dental care are two of the most important things you can do to keep your little one healthy and happy.
