As we're all terribly aware, Frankie of The Disreputable History of Frankie Landau-Banks is a girl. She's a rather pretty girl, having grown into some womanly curves over the summer, but she's still just a girl in the eyes of certain people (ahem, Matthew). And because of that, she's excluded. She can't join the Loyal Order of the Basset Hounds, she can't come along with Matthew when he's hanging out with Alpha, and she definitely can't be privy to any of their secrets. It's quite the bummer, but she figures out a way to make it work.
Frankie's In Ladies We Trust prank is the first time that she examines the role of women at Alabaster, and it sets off all her other pranks.
Frankie wants to be with Matthew but not at the cost of her own independence, and she has to learn to stand on her own two feet over the course of the novel.