Oh Cass: I just read your post, and I am in tears for you. You did absolutely everything you could for her. Coco is now running well and feeling great at the Rainbow Bridge. You are going to feel so lost without having to spoon feed, watch over her, and everything else you did.
I wonder if the vet did a necropsy on her? As a medical person it would be interesting to find out just what this was. I certainly understand if you did not---.