"Well kiddo i thought you outgrew superstition"

Mister Babadook, Laurie is remembering that it is the horror holiday and trying to use that as a way to avoid what she senses. She means that the younger kids are just having fun with the monsters, especially since they might believe that some of the latter are real, and is comparing herself to them. Michael Myers' sister feels silly for carrying the impression that an otherworldly creature is chasing her because she knows that there is no truth to the tale about such things happening on Halloween.