Yup, for a while we’ve been surmising that Lizzie is the little psychotic. Looks like we were right. So great if Carol comes back! I really would like to see that. It makes sense, since she’s “adopted” Lizzie as her own, that she would have to be the one to “put her down,” me thinks....
Carol covering up for Lizzie makes sense. However Carl is also a possibility. After all, he’s already killed the living when he didn’t need to.