Earlier quoted context omitted.
> If there was ever a win-win situation, this is it. Say what? She lies via omission to the parents, forcing them to make an uninformed choice. Instead of letting a rabbit loose in the wild, they might have sought another home for it, because they didn't want it to die. Your sister's lies mislead them into thinking they can safely return the rabbit.
Letting them free will likely get them eaten anyway, probably less humanly since they’ll still be alive while they are eaten. Or run over. These are domesticated rabbits, not wild ones.
Rabbits are good as prey, great as pests, bad as pets.