Ask me this on three different days and you'll probably get three different answers, but right now I'm feelin' Dusty because her metanarrative role as "the not-as-important one" tickles me immensely. Despite originally being envisioned as a way to backfill the flashback/present day chapter structure and flesh out the setting and Lou's character, the maid chapters have ended up introducing some extremely important characters—Sleeves is pivotal in Act 2, Chiffon is a crucial emotional support for Lou and looks to be increasingly relevant in Act 3, even the at-the-time-unnamed guard who stumbled upon Lou in the halls has gone on to be the storied Soixante Douze.
But not Dusty! Sleeves and Chiffon both know Lou's secret, but not Dusty. Sleeves and Chiffon have both left the city to seek adventure, but not Dusty. Dusty just stays Dusty. She's the archetypal friend in the group who's kind of out of the loop, doesn't really participate in the group chat, but who everyone's glad to see during the reunions. Dusty abides. And I love her for that.