Ah, one thing I remembered right off; you can try prozyme, its a dietary supplement that helps with digestion.
Prozyme is a plant-derived enzyme supplement. It helps to digest protein, fat, sugar, starch, and fiber, as well as helping your cat break absorb a number of vitamins and minerals. You'll also find your cat will likely need to eat less and thus go to the bathroom less, which could be very helpful. :)
If the stool is nice and firm she just has a good intestinal system. Count yourself lucky she doesn't have mega colon problems.