What's she eating, Liz? If it is a strain of gastro that will probably have stripped her gut a little bit, which will make it harder to digest her food properly. Giving her more non-fibrous food for a little while might help. Things like white foods (bread, rice), noodles, banana, crackers. Of course the breastmilk is tops for it as you know.
I'd try restricting the diet to non-fibrous stuff first and then if it still keeps up I'd have a trip to the drs just in case.
Hope she is better soon.