She's obviously sick, but those fluffy bunnies aren't pets, they're food.
The two people she killed in the prison though, weren't food or pets. Yes, that's my prediction. Little Lizzie killed the two sick people in the prison. Carol found them, possibly while she was still joyously carving on them. Scolded the girl, took the bodies out and burned them so no one would know they'd been carved up. Then when Rick confronted Carol she wasn't going to turn in her beloved little girl, because she didn't want her locked away or killed like the psycho she is.