For the majority of their stint on the run, Carol and Tyreese didn't seem to realise that there was anything actively dangerous with regard to Lizzie's confusion about the differences between the living, dead, and undead. After seeing Lizzie playing tag with a Walker that she named "Griselda" (after Mika's doll), however, they might have wanted to put her under a bit more supervision. Lizzie snaps when Carol sticks a knife in Griselda's skull, shrieking that she and the zombie had been having fun together. Carol had killed her "friend," says Lizzie, and to kill Carol would be no different. Both Carol and Tyreese are clearly unnerved by Lizzie's breakdown, so they naturally work out a schedule to ensure that at least one of the adults would be with her and the other girls at all times to prevent further incident. Well, that's what should have happened. Instead, Carol and Tyreese developed a habit of wandering off and leaving all three of the youngsters alone together. Mika was already established as unwilling to hurt another living person, Judith could neither walk nor talk, and Lizzie was growing more and more desperate to prove to everyone that Walkers were just people who were different. This turned out to be an unfortunate combination, and only Carol's and Tyreese's timely arrivals prevented Lizzie from killing Judith as she had already killed her sister. At least Rick would have been right about Carol being a danger to his children. Lizzie may have been a ticking time bomb bound to explode on somebody eventually, but Carol and Tyreese really ought to have kept a closer eye or any eye, really on the kids. Oops?
Fiction buff and writer. If it's on Netflix, it's probably in my queue. I've bought DVDs for the special features and usually claim that the book is better than the movie or show (and can provide examples). I've never met a TV show that I won't marathon. Follow on Twitter @lah9891 .