If the change in food is responsible for the changes in her stool there are two possibilite. First, any change in diet can lead to a change in the chemistry (esp pH) of the GI tract which results in a shift in the bacterial balance, this can take a week or two to settle downnnn. Second there may be more fiber in the new food which leads to higher stool volume. It's not clear if there has been a change in the charaxter of the stool,ie softer, mucus, diarrhea, etc. If the stool is normal in character I would go back to the other food for a week or so and see if the stool changes with it, iif it does not you may want to get her stool checked by your vet. I assume she has been previously checked and is on a monthly parasite prevention product. Please send any other questions or clarification through the forum.