It sounds like it could be pyoderma, aka an overgrowth of staph intermedius - which is an infection that is treated w/ Simplicef x 30 days. Often, pyoderma is secondary to allergies. If she chews/licks her paws at all, this is a sign of allergies. They should do a skin scraping at the vet to determine pyoderma, very simple.
More about allergies here:
http://www.yorkietalk.com/forums/die...tart-here.html