Good luck for the vets, how long has she had kidney problems?
With regard to shorter but happier life, my old boy, Harry, I got when he was 10 from CPL (age an estimate as he had been a stray). He had to go on to steroids from the off as he had a severe skin allergy. They said long term steroids would shorten his life but like I say he lived until 19.
I think he started with kidney failure at about 16 so he had a good few years at a fairly advanced age on the steroids, kidney meds and finally also permanent antibiotics as he had a mouth infection from a growth but he was too old for an op to remove it. He was very much one for sleeping on the bed, preferably on my pillow, which was great with the bad breath that the mouth infection gave!