Seven

From Jenny Everywhere Wiki

Seven was a mysterious girl who once showed up in the Foyer of the Strange and Wonderful House, following Six, who was afraid of her. Six and Seven played out their iteration of the chain of events which kept repeating inside the Foyer with different visitors as a duo, opposite Eight. In the time between Eight ducking out of the Foyer and knocking to come back in as the pattern dictated, Seven apparently ate Six. When Eight expressed confusion about where Six had gone, a grinning Seven denied having ever known anyone by that name. (PROSE: Our Strange and Wonderful House: The Foyer, Foyer Infinity)

Behind the scenes

Six, Seven and Eight in Our Strange and Wonderful House are a reference to the joke “Why is Six afraid of Seven? Because Seven ate Nine!” (i.e. “Seven Eight Nine”). Six being afraid of Seven from the start suggests that the joke's narrative, such as it is, occurred prior to the beginning of the Foyer trilogy.