If you like Fromm, you could just switch to the Fromm Four-Star Grain-Free line: Four-Star Gourmet Recipes for dogs - Fromm Family Foods
as that would likely cause minimal digestive upset, and you could see if it solves the problem, before switching to a totally different food line. Just a thought.
The allergy could also be to something other than food. Do you wash your floors or her bedding with any chemicals that might not agree with her? Does she spend time outside in the grass?