Is it k/d? Cause I know A LOT of cats that refuse to eat k/d. There are definitely a few renal diets out there (Purina makes one, Eukanuba makes one - check out felinecrf.com for tons of info) but I recommend Royal Canin Modified Formula. Until about two weeks ago I could have honestly said that I never knew a cat that turned it down, but of course there had to be that one who would make me not be able to ever say that again. But not much can be said for her taste as she chose to eat the k/d over this magical food. Seriously, that's what we call it at my practice, "Magical Modified" because (almost) every cat will eat it. It has mackerel in it which I think the cats can really taste and LOVE. Plus, you can always add a little chicken broth to any canned food to increase water intake and make the food a little tastier for our finicky friends.
I prefer most Royal Canin therapeutic diets over the Hill's RX diets anyway. I think they are much more palatable and have higher quality ingredients with less by-products and preservatives. I actually have my cats on the Calorie Control diet.
OK, I'll stop going on about the RC therapeutic foods, but seriously, try it! You don't need a prescription for it like you do for the Hill's foods but you do have to buy it from a veterinarian. If your vet doesn't carry it, call around to other vets in the area or call Royal Canin and ask them where the closet place is where you can buy their products. (800) 592-6687. If there is a bigger emergency hospital in your area they should carry it. I don't know where you live so I can't really help you out with that part, but good luck and I hope she likes it!
Oh, there is also another Royal Canin renal diet called LP but I don't think that goes over any better than the k/d chicken as far as flavor. But it does come in pouches so it's more of the chunks and gravy deal than the regular mushy food so if your cat is into that sort of thing, they may prefer LP & you might want to try that.