I am so sorry to hear about Sadie....
Liver shunt has a number of causes - it may be congenital, which would reflect badly on the breeder.
I am shocked the breeder gave her a vaccination when she wasn't well... this is a major no no! Vaccines affect the dogs immune system, so should NEVER be given if the dog is not in perfect health as it can give their body too much to cope with at once.
Still, at least your mom has agreed to get Sadie whatever vet care she needs. Will keep everything crossed for you, and hope she gets well soon!