Posie is a character who has yet to appear in Everafter.
She is the twin sisters of Rosie though they look quite young, they have been in the halls of Everafter longer than any of the other inmates.
"Ring a Ring o' Roses" or "Ring Around the Rosie" is a nursery rhyme or folksong and playground singing game. It first appeared in print in 1881; but it is reported that a version was already being sung to the current tune in the 1790s. It has a Roud Folk Song Index number of 7925. Urban legend says the song originally described the plague, but folklorists reject this idea.