fight of the living dead theory
i think Cynthia was in a project where they tried to have a person be able to command the zombies on their own without getting eating and she was the test subject of that project and only could get to where the zombies saw her and one of them but nothing else cause she was to traumatize from the testings she was put through and in order to not just kill her off seeing how she was a partly successful project they decided to use her within the experiment 88 layout
my proof: in the interdiction video the team had gotten in the first episode it was talking about conop and that they mention about making zombies into weapons: they probably need some sort of way to control them before the sound system was stabilize so they tried using humans in a sence to try to control the zombies
also there were 2 times we seen zombies going after the survivors and not Cynthia we even seen in the last episodes (spoilers in case anyone haven’t seen last episode) that she stayed behind and stopped her dead doctor friend from getting to the rest of the survivors and at the very end of the episodes we see her with no bite marks and not looking dead coming out of the shadows
and this would explain Cynthia’s child like behavior as well cause one could be so traumatize depending on how they did their experiments that she could just end up like staying child likeÂ