Your aunt needs to do some serious manipulation of this woman!

One possible idea - have your Aunt say to the breeder "you've taken such wonderful care of Hazel - but you have so many other kitties to take care of that I can take her home for her final days so that you don't have the stress and worry of her infecting any of your other precious kitties"

then she should get that kitty the h**l out of there and to another vet!

(prayers on the way!)