Update.
I've had CC 2 weeks now. She was eating Hills kibble with Hill canned for flavor supplied by the adoption group. She really wasn't interested. So I canned the canned for homemade to be mixed with kibble.
Ok that was a huge hit. Eating better. It's a mix of veggies, pasta and either chicken or eggs.
I took her to my vets who was appalled by her mouth (as was I). He said it was definitely a contributing factor if not the actual cause of her kidney issues. He also said the values weren't bad enough she couldn't handle anesthesia. The adoption group was afraid to give her anesthesia, thus no spay or dental. They have a clinic on site. So it was their vet that nixed it.
But I knew her mouth would affect the rest of her body, so we did the dental.
She survived, lost 24 teeth.
She now finishes her food, twice what Emma gets faster than it takes Emma to eat. And Emma is a champion food hound. It's very obvious her mouth was painful. But she's feeling great now. And my vet said to not judge her kidneys until we get another set of bloodwork in 3 months.
So I'm being a little optimistic that with a clean mouth now, her kidney values will improve.