How much rice are you feeding her with the chicken? Sounds like she might have too much rice and not enough chicken in her food. I am confused why the vet thinks that you should do the canned and not the boiled chicken and rice. I thought that was pretty standard with the diarrhea issues.
If you feel her poop is firm and her tummy is settled you should ease back to her regular diet at some point. You should also look into a vet that believes in a raw diet otherwise you are going to be fighting a losing battle with your current vet.