I'm so sorry this is happening. I've gone through similar things with beloved pets and it is always deeply heartbreaking.
As has been suggested, try to make the most of every minute you have with her, doing anything she wants to do. Give her tons of loving, although you probably already are doing that.
Take pictures!! Take video!! One thing that still makes me sad, even though I now have another cat, is that I don't have more pictures of my two previous cats, and I have zero video footage of them. I shoot lots of video of my present kitty now.
I really love the pet hospice care idea. I have never heard of that, and I really wish my one kitty I had to put to sleep for kidney failure, on a cold steel vet table, could have passed in the comfort of home instead. It sounds like a much better idea and I wish there'd been a service like that when my darling had to go.
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