Mirren Sinclair Sheffield is one of Cady's cousins. Mirren lived in Cuddledown with her mother, Bess, and her siblings, Taft, Liberty and Bonnie for most of her life but in summer 17 her mother, Bess moved to Clairmont with her siblings; Johny and Gat moved into Cuddledown with her. Cady first describes Mirren as 'sugar, curiosity and rain.' Mirren lives in Cambridge when not on the island.
"Be a little kinder than you have to."
- "I have a boyfriend named Drake Loggerhead. He's going to Pomona like I am. We have had sexual intercourse quite a number of times, but always with protection. He brings me yellow roses every week and has nice muscles."
- "There is not even a Scrabble word for how bad I feel."
- "I got one chance to be here, and I don't know, I drew it out, told so many lies."
- "I want to be an accepting person, but I am so full of leftover rage. I imagined I'd be saintly and wise, but instead I've been jealous of you, mad at the rest of my family. It's just messed up and now it's done."
- "Gat was right, as usual. You're always effing right, Gat. Girls don't like that in a guy, you know."
- "You know how, when you come to Beechwood, it's a different world? You don't have to be who you are back home. You can be somebody better, maybe."
- "That first day you came back I noticed Gat. He looked at you like you were the brightest planet in the galaxy." " I want someone to look at me that way so much, Cady. So much. And I didn't mean to, but I found myself lying. I'm sorry." "Don't gasp. Okay? It's fine. It's fine if I never have a boyfriend at all. It's fine if not one person ever loves me, all right? It's perfectly tolerable."