Annette Barniel, a Swiss girl from the mountain village of Rossinière, experienced profound loss when her mother died during childbirth on Christmas Eve during Annette's seventh year. This tragedy left her responsible for her newborn brother, Dani, forcing her to temporarily leave school and manage household duties until her great-aunt Claude arrived to help. Annette formed a deeply protective bond with Dani, effectively becoming his primary caregiver.

By age twelve, Annette possesses a complex personality. She excels academically, ranking among her class's top students, and demonstrates domestic skills like sewing, though she initially struggled with cooking. Her temperament blends sweetness with volatility; she is generally well-liked yet prone to anger, commanding respect even from school bullies due to her fierce determination. She maintains a tomboyish, outdoorsy nature while embracing traditionally feminine tasks, often wearing a pink dress. Her closest friendship is with Lucien Morel, a bond rooted in early childhood, though frequently strained by arguments and reconciliations.

A pivotal incident occurs when Lucien accidentally causes Dani to fall from a cliff during a confrontation. Though Dani survives, he sustains a permanent leg injury requiring crutches. This tragedy profoundly alters Annette. Her protective instincts curdle into intense resentment towards Lucien. She openly blames him for Dani's condition and coldly rejects his reconciliation attempts, even destroying a meticulously carved Noah's Ark he made for Dani. Her bitterness escalates further; driven by jealousy over a school competition, she deliberately ruins another of Lucien's woodcarvings, a prancing horse intended for Dani. This act triggers a profound moral crisis, forcing her to confront her own capacity for cruelty and recognize parallels between her actions and Lucien's original mistake.

Annette's development centers on overcoming this deep-seated resentment. Overwhelmed by guilt after sabotaging the horse, she confesses to Lucien and begins a slow emotional reconciliation. Her protective love for Dani remains central, motivating both her initial hostility and her later relief when Lucien arranges a life-changing surgery that restores Dani's mobility. This resolution enables her to fully repair her friendship with Lucien, moving from hatred to mutual forgiveness. Her journey underscores themes of accountability and the corrosive nature of grudges, contrasting her initial refusal to forgive with Dani's innate innocence and lack of malice toward Lucien.