Hi and welcome to YT
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This could be just a summer tummy bug that will take a little while to go away. But I think I'd take her to your regular vet and get a blood chem panel done, just to be sure her major systems are looking okay overall.
To stim her appetite, I'd try making some baked white potato (or use canned), with a bit of butter spray on it...topped w/ some Parmesan cheese.