Make sure she understands that SHE would have to clean the litter box.
She's 20 and very good about cleaning stalls and shoveling poop. But the poop issue was not the way I talked her out of the sheep. I just pointed out that we own a hunting dog who regards everything on four legs that is not canine as lunch, and he would be absolutely delighted with the gift of tiny sheep.
I don't think he'd be stupid enough to tackle a moose, though.