The vet should have tested Kiwi before putting her under. There is a blood test they can do to see if they will have problems. Unless you refused it, it should have been offered. I also agree, why did the dog need to be under for checking it's cast?
You could pick up Kiwi and take her to another vet and her an autopsy done, to see if there was something really wrong with her liver, or too much anesthesia or ???
I am very sorry for your family's loss. She was adorable.