She's losing her baby teeth and getting adult teeth. There's the problem of a gum pocket where the baby tooth is missing, food can get in the pocket and mixed with blood, it's not a good odor. Also, for some dogs they get their permanent teeth before they lose the baby teeth and will have a double row of teeth and food gets in between the rows and rots. I use Petzlife Spray and Joey also chews on hard bully sticks to help scrape teeth of tartar. I also brush his teeth a couple of times a week, but I'm not sure if there is a lot you can do while they are teething. The smell goes away when the gum pockets heal. Now is a good time to get them use to toothbrushing!