I am so sorry about Ashley.
Kidney failure with kitties is so hard because if you don't catch it soon enough, its downhill from there. My first cat died from kidney failure and my furbaby, Boo, has kidney troubles. We take him to the vet yearly (sometimes more often) for checkups. I'm not letting kidney failure happen to him.
I hope you can find it in your heart to make room for another kitty soon.