Aww I hate posts like this, my old cat had to be put to sleep on 1st Dec, he was 18 and had pretty much the same trouble as your cat, but he still managed to reach his litter tray although it was an effort for him. I was very reluctant to have him put to sleep but the last day of his life he couldn't even lift his head up to look at me. If your cat is still eating and drinking and plodding about then just try a litter tray, only have her put to sleep if she is suffering or obviously not enjoying life anymore. It could be near the end for her who can say. My thoughts are with you because I know how hard it is. puss xx