I can relate to all of these posts and know we are all just so blessed to have our pets. I am also a cat lover and have a little one who is somewhere between 18-20....not quite sure. I took her to the vet over a year ago thinking her time had come too....she had irritable bowel syndrome. The vet gave her a shot and I began feeding her duck in the can (I read on line that this can help). She appears to have no more symptoms of the IBS and I now can feed her other things. I am posting this about the diet in case anyone else has gone through something similar with their pet.
I am sorry for your loss and hope you can dwell on all the sweet memories of your precious kitty!