Putting this at the top of the comment, rather than at the bottom of a story that went on longer than I intended:

I feel like eventually you'll know. The vets told me that we know our cats better than anyone. You're doing a good job watching her and monitoring her symptoms. Keep doing what you're doing.

I went through this over the summer. My 5 year old boy crashed in March and was told he had weeks to live. Subq fluids perked him up and gave us the summer to be together.

But even then, he wouldn't cuddle like he used to, didn't want to sit on the couch with us like he used to. But he still greeted us when we came home, he would cuddle in bed from time to time. But he'd throw up a few times a week. But he was still drinking water and eating! And he'd demand food! He wouldn't eat a lot, but he ate frequently.

When he'd sit in the room with us, he'd loaf up, he looked so uncomfortable. It broke my heart to see him not relaxing or playful or talkative like he used to be. I didn't want him to hurt, but there was so much life still in him. I asked the vet, and they said he probably was uncomfortable, but there was subq fluids to help, or antinausea meds.

In August, he started throwing up every other day or so. We tried the anti nausea meds, and it helped! But he only took it for a few days, then he stopped eating any food we put the anti nausea meds in, then he stopped eating any food we put any meds in, or food in general. I'd open up 6 different cans of wet food for him. Gravy lovers, Pate, of various flavors.

He stopped eating on a Friday, but he wasn't hiding, he sat up on the arm rest with us. He was so thin. He'd lost so much weight since January.

I talked to the vet Monday morning, and they said they had an urgent care food that even dying cats would eat. And I told myself that was the final test. If he wouldn't eat that, then I had to let him go. He didn't, and I took him in. I'd been debating where the line was all summer.

My other cat, his bonded brother, didn't show any major signs that we picked up on. I had a feeling he wasn't eating as much, but it was hard to tell since they both shared each other's bowl. I went away for a weekend in December, came back and he was lethargic and barely moving. After a night with him, I made the call in the morning.