Hello and welcome to Just Answer,
Thanks for your question concerning your puppy. I need some additional information to help out.
1) What breed of dog is it?
2) What brand and type of food do you currently feed?
3) Are there any sores inside her mouth, or is she loosing any puppy teeth?
Reply back and I will help.
Ok, thanks for the additional information.
If she is loosing some puppy teeth, often they will have some bad breath. With that said, bad breath can also be due to other metabolic problems (i.e. kidney disease etc).
If her breath is not improving in a few days, then I would recommend that you have your veterinarian check her out just to be sure. It is better to be proactive and safe, then let an underlying problem continue.
I hope this helps, and let me know if you have additional questions.