Most of the gravy-type canned foods are pretty high in carbs. Friskies shreds/chunks are made mostly of wheat gluten. I wonder if she's gluten intolerant? That would make a lot of sense, actually, because some of the symptoms are gas and bloating. Try a paté-type food (preferably a high-quality grain-free like EVO, but if that's not an option the Friskies paté or Fancy Feast Classic should be OK) and see if anything changes.