If she was fine on the food before the giardia, it's probably not the food. You might need to build up all of the good stuff in her gut again. Get her on a good probiotic. This is a fantastic supplement for soothing the stomach (which may just be inflamed after all of the problems):
Altarulm | Chinese Herbal Remedies | Qi Herbal Apothecary
If you can't find it, look for the individual ingredients in a health food store (slippery elm, marshmallow, and licorice).
Edit: I should add that the food might not be too rich for her in general, but it might be right now while her stomach is inflamed. You could give her a couple of days of a bland diet (canned pumpkin, cottage cheese, yogurt, could also do boiled chicken and some people feed rice) and slowly work the kibble back in.