She would have died if she hadn't gotten the transplant at all.
And since the transplant wasn't the right blood type, then she wouldn't have gotten that FIRST transplant either, would she? She would probably STILL be on a wait list, so she COULD had already died by now.
And once she GOT a transplant, there's no guarantee that she would have survived.
And even if she DID survive the transplant, there's no guarantee that she wouldn't have walked out of the hospital and gotten hit by a bus.
That's still no reason why her parents couldn't donated what could have been harvested - at the minimum, skin is very useful for burn patients.