Oh Joan, I was given the same choice on Saturday morning. My elderly cat had been telling me half the week that she was ready to go but I kept thinking she would eat something if only I could find the right food, she just had to to take her medicines, and she would drink enough to keep going. I decided on Saturday morning that it just might be her teeth and took her to the vets immediately.
Luckily they let me wait. The vet looked at her and said her teeth weren't too good but due to her age (almost 19) they wouldn't guarantee a successful operation and she didn't think that was the cause of her not eating/drinking.
But why didn't I have some blood tests done to see if there was any change in her kidney problems. If it had got worse, and she still wouldn't eat over the next few days, she could be put to sleep sometime this week, and if the blood tests were ok, they could operate on her teeth this week.
Initially I decided to have the blood tests done but suddenly I looked at her and thought I'm only doing this for me. She would have had to go to the hospital for the weekend no matter what, for rehydration, and I just couldn't bear to take her there, all upset and bewildered, and leave her there all weekend, so I decided to let her go there and then.
She weighed so little, and was so weak that I thought she should go in my arms with me kissing her.
I have felt guilty ever since but I absolutely know I did the correct thing, and so do you, you have tried all you can, no one could have done more for her, she'll be at peace, bless her.