That's some backwards logic. Maybe she's stuck on the "snakes eat cuter fluffy animals" track.
I have a friend who is strictly vegan, but is fine having pets that are strictly carnivores. She knows that while humans have the anatomy to digest a plant based diet, carnivorous animals do not, no matter what their owner's morals are.
Just the fact that there are vegan cat foods is rage-worthy. "Vegan" cats have to have constant urine tests just to verify you're not killing your cat yet. Even then, blindness is very likely.