Thank you all. It's been a very long few days, but Zoe did pass early this morning. It was peaceful. I'd slept in the living room the past couple nights because I didn't want to move her back to the bedroom. At 6 this morning DH sent me to bed to take over Zoe watch. About 10 minutes later she let out a couple quiet gasps and was gone. He came and told me that she apparently waited for me to leave, and he probably was right. They, just like people, will hang on for you. After it stops deluging outside we'll take her to be cremated.
It was hard keeping her here so clearly fading, but the kids got to come say their goodbyes and she was never in distress so I think it was the right call. In some ways easier than taking her to the vet. I think it was easier for her.
I really appreciate the comforting thoughts the last few days.