How heartbreaking!
My Fletcher had HGE back in July, but it was nothing that severe. They did blood work and he was borderline, so they told me to stay close with him and if he gets worse, they were going to admit him and get him on IV fluids and antibiotics, but luckily the SubQ fluids along with canned bland food, probiotics and antibiotics, he recovered at home with me caring for him in about 4 days. He ate duck poop, bird poop is so bad for dogs, it's FILLED with nasty bacteria. We have ducks that land on our pool sometimes and I think they might have pooped and he ate it, without us seeing it.
Its just awful to see them so sick and wanting to be with them but knowing they are better off with the vet. I'm like you also, there is no limit to what I wouldn't do for my boys, I would be in the ER all day on Christmas as well as the $4000+ in bills.
I pray she keeps improving and getting stronger and able to come home with you very soon.