What are you feeding? There is a recall on Innova and other dog food made by Nutura.
Have you changed her food during this time?
Try a teaspoon of PLAIN canned pumpkin a couple of times a day. Feeding boiled lean hamburger or boiled chicken with white (not whole grain) rice is sometimes recommended.
Are you giving her any treats or is there some new treat or 'people' food you have recently started?
Probiotics might help, here is a link to an article from the Whole Dog Journal.
http://www.whole-dog-journal.com/issues/15_3/features/Probiotics-For-Dogs_20473-1.html