Millie Calloway is introduced as a vulnerable yet resilient character with a strong instinct for survival. Estranged from her family, isolated after a long prison stay, and forced to live in her car after being fired from her job, Millie has a deep desire for belonging and stability. Her initial resentment toward Nina is rooted in her longing for the life Nina seems to have—a stable home, wealth, and a family, all things Millie has lost.
Millie’s survival instincts and her history of vigilante justice gradually reveal a darker, more complex side. Her outward submissiveness hides a fierce moral code, driven by a deep sense of justice. Millie’s past is marked by acts of violence, but her aggression is consistently tied to defending herself or others from abuse. She was imprisoned after killing her friend’s rapist in a brutal act of self-defense, and many of her other violent outbursts are similarly rooted in situations where she is forced to act. Despite her violent tendencies, Millie has a strong sense of right and wrong, though her methods can be extreme. Her survival instinct often blurs the lines between victim and aggressor, especially as she begins to turn the tables on her abuser, Andrew.
By the end, Millie fully embraces her capacity for violence, turning her own traumatic experiences into a weapon. Her transformation into a protector complicates her character, as she steps into the role of an oppressor and enforcer to regain control over her life. Her story concludes with her poised to continue in this new role, as the novel hints that her journey of survival and vengeance is far from over.