I'm so sorry to hear about your kitty ): even though I'm super late, I saw this thread tonight and figured I would offer some advice.

Two years ago, my mom and I had to watch one of our kitties die- she was the younger of our two (13 when she passed). The best thing you can do if you know they are dying is to keep them happy and comfortable. Our kitty was losing weight very fast, and had a strange lump on her back. We kept her comfortable by putting out a lot of pillows and blankets that were soft, and helping her onto them. We bought her the "fancy" cat food, which she enjoyed on occasion. We kept her happy and comfortable until the end, and she went out purring like a little motorboat. It's not easy, which you know, but help your kitty as much as you can, and keep your cat comfortable and happy when she's declining. That's the best thing you can do for them.

I am so very sorry to hear about your cat love. Losing a pet is NEVER easy. We love them like they are our own children. And it hurts ten times worst around the holidays. We had to take my grandmothers cat to the vet last night and had to put him down.. :( We unfortunatly did not know what was wrong with him because we did not have the money for all the tests they wanted to do on him.. He was 18 years old. The vet guessed that it was renal failure. (Kidney)

Stay strong love for Miss Peepers!