We have a ~15 yo rescue (age is estimate). When we rescued her she was already decrepit, had severe dental disease and had to have all her teeth out, had been mistreated and neglected so was very feral, is pretty inbred, and has cat asthma. Not a great start in life.
We've had her about 5 years where I think she's been pretty happy.
In the last year she has massively deteriorated, i.e, going to the toilet anywhere, cat dementia (constant loud meowing), less mobile, not grooming herself and needing clumps of hair be shaved otherwise she rips her own hair out, forced grooming to remove urine/faeces off her back end, deafness and lashing out at us and the other animals. Although she's tame and quite sweet she wont be brushed or take medication without a fight. It's getting hard for us to manage and our other pets are getting visibly stressed out by it.
Naturally I consulted the vet who said that her age has caught up with her; she is deaf and has dementia, and there's probably some underlying age-related illnesses like hyperthyroidism which is common in older cats and while medical intervention might prolong her life ultimately it is our decision but they would be satisfied if we decided to put her to sleep now or if we wanted to extend things as long as possible.
To make matters worse, DH gets all the good bits. The cat snuggles with him whereas I'm the one who empties the tray, feeds her, intervenes when she goes for the other animals, washes the soiled furniture/bedsheets/carpets, gives her medicine, she follows me around howling for hours and the sound is driving me insane!!! DH is aware of this so he said 'it's entirely your decision sweetheart' and now it's like the cat knows and is being uncharacteristically attached and soppy with me and I have the mortality of this animal on my conscience. And I have no idea what to do. We couldnt get great insurance on her because of her age and background when we adopted her to there's a limit to how much that will cover.
My mum said it's better to put them to sleep too early than too late and I need to think about my well being, but what if I do and it's the wrong decision. :/ The cat might live another 4 years but then I don't think I could take another 4 of the sofa smelling of cat wee. How do I know what's the right thing to do?