but there was a time jump between seasons, judith went from being like 3 to 9 when maggie left
edit: just looked it up, maggie was in a few of the episodes after the time jump so it makes sense
nah Maggies last Ep was Ricks last Ep, she was just around for a few years after that, which is why Michonne is shocked to find out Maggie left when we catch back up with them in the time jump, Judith was probably somewhere around 5/6 age wise when maggie left