I am so sorry to hear about this! You were obviously right to be concerned and it does seem like maybe she shouldn't be allowed to have pets. I know that she is your daughter, but have you thought about reporting her to the Animal Control in her area? I know people have indoor/outdoor cats, but letting a cat outside unsupervised is actually illegal in a lot of places because of exactly
what happened in this situation. I don't know what kind of action can be taken after the animal has already been killed (sadly :() but maybe a fine would teach her a lesson?