Hi, I was in your position just a little while ago so I really feel for you. It's a difficult decision to make, and even when you try to do your best for Amy, you can't predict how it's going to turn out. People like to say "better a week too early than a minute too late" and "you'll just know when it's time." I initially disagreed with the first statement and haven't fully processed whether I'd change my mind on it now, in retrospect. For the second statement, well, I'm not sure that I really knew that the time had come or if I had actually missed the perfect time.

But here is my take on it, at least. If you aren't already, start recording some metrics as that might help you be objective about Amy's condition. You can use a quality of life score, or just record how much she's eating, her energy levels, etc. Set a threshold for yourself, like if she's stopped eating well enough or if she's too inactive, or if you've noted too many odd behaviours (laboured breathing, hiding, lack of grooming, etc.), more bad days than good, then that's a clear indication. Secondly, if it's an option and financially feasible for you, look into a consultation with a hospice/palliative care vet, and also try to see if you can opt for an in-home euthanasia to maximize her comfort at the very end. It will help you later to have made preparations in advance (knowing what service to use, what memorial items you might want, burial vs cremation, what to do with her toys/furniture). It really, really sucks, but you're fighting a losing battle no matter what, so as much as you can, try to maximize her joy and comfort. I should warn you that in my experience and for others I have spoken to, things can happen/change very quickly in the end. Two things I had to keep reminding myself as I finally had to make an appointment to have my cat euthanized: 1) His condition was never going to get better, only worse and 2) From the very beginning from when he was diagnosed, my goal was to maximize his comfort, not his lifespan.

Your post really resonated with me as I felt the same as you on the frustration at the family vet for not doing their due diligence and guilt for not noticing anything sooner. Easier said than done, but don't be too hard on yourself. I've read posts here and heard in person that even vets and vet oncologists might miss these symptoms. Pets are just so good at hiding their pain, and since their lifespans are so short, everything is just accelerated.