Chronic Diarrhea in Dogs good article, describes all the testing available to determine causes of chronic diarrhea. I would go with the probiotics and food change, if that doesn't help, work with your vet to develop a plan of what to test for first. My first concern would be her weight and hydration. Keep a close eye on her, as the more info you can provide the vet the better. Color, consistency, frequency, in relation to eating and exercise, etc. any changes should be noted. As you change her food, keep track of what ingredients you are eliminating/adding and any effect on her systems. Good luck, and keep us updated!