Should I try to re-train my cat, or just leave her be?

There is medication you can give Stay to help her with the stress and hopefully feel like her hold self. You should also train Ajah to not aggravate Stay so much (it CAN be done). We have used Aconitum Napellus 30 with three different cats with great success. It's a homeopathic medication that can be found in may health food stores. Give Stay ONE pellet up to two times a day. It's easier than most meds because the pellet is so small. Aconitum helps with stress, anxiety and grieving. For Ajah, a squirt gun or squirt water bottle may work to re-train the kitten. (and two litter boxes for a while at least may not be a bad idea).

You really didn't make a good choice in your timing to bring a youngster into the house. At 18 she deserves better than to be deviled by a kitten. You said the kitten was chasing Stay - of course she's staying on the couch and not going to the litter box! The kindest thing is to rehome the kitten, and not get another until Stay passes. Her new behavior isn't "odd" it's stress.

She isn't happy about the kitten. And she is telling you the only way that she can. You can't re-train her because she doesn't think she is doing anything wrong. A new kitten with an elderly cat wasn't a good idea. Try to provide her with a room that only she can access even if this means locking her in and the kitten out. Those pee pads on the couch are a good idea but expensive. You can buy fabric pads that they put in the beds of people who lose control of their bladders - you need to wash them when they get too peed up but they are a good solution money-wise. |If you had two pads one could be in use and one being washed.

Put a second litter pan in a different area of the house from the first area. The kitten cannot be in two places at once.

Also take your old cat to the vet. She may be suffering from kidney failure, the #1 most common ailment of elderly cats (& the #1 killer of elderly cats.) If she has kidney failure, she may not be able to make it to the litter pan or she may not feel well enough to go all the way to the litter pan. You might try putting a litter pan behind the couch and see if she will try to use it. If your cat has kidney failure, the sooner she is treated by the vet the better. With supportive care, a cat with kidney failure can still have some quality time left.

Pictured is my oldest cat Mew, who looked very much like your Stay, died of CRF (chronic renal failure) when she was almost 19 years old. In this picture she was playing with the camera strap. The picture was taken 2 1/2 weeks prior to her crossing the Rainbow Bridge.

Well I don't think you should change her name at all because the cat got used to her first name so now it's gonna be hard for her to get used to her first name...

Hope this helps