The show is unclear on whether they’re actually dead or somehow otherwise magical. Every iteration gets to fashion its own rules. I think the explanation in the Night of the Living Dead movies is that hell is full. Or maybe that was just for one of them. Anyway, The Walking Dead has it as a disease, and everyone’s infected. People seem to die first then wake as zombies, but you can’t be sure.
Haven’t seen the show, so I probably really shouldn’t be commenting on it. Though that never seems to stop anybody.
The relevant point is that one doesn’t have the option of taking in that poor, pitiful, hungry, dirty feral child and caring for her.
She’s hungry all right, and it’s for your brains.