Born on June 16, 1817, Azelma Thénardier is the second child of the Thénardier couple. Her older sister is Éponine, her younger brother is Gavroche, and she has two unnamed younger brothers. Azelma first appears as a young child during Fantine's arrival at her parents' inn with Cosette. At this stage, influenced by her spoiled upbringing and the encouragement of her sister and mother, she mimics their cruel behavior toward Cosette, acting more from following their example than from inherent malice.

As the Thénardier family's fortunes decline, Azelma moves from a privileged childhood into destitute adolescence. During her teenage years, pressured by family and survival needs rather than personal ambition, she participates in her father's criminal activities, such as delivering letters to wealthy targets to extort money. Unlike Éponine, Azelma shows no defiance toward her father and complies with his demands, including breaking a windowpane to feign poverty during Jean Valjean's visit – an act that cuts her hand.

A significant turning point occurs when Azelma is arrested while keeping watch during Thénardier's attempted robbery of Jean Valjean. She spends a substantial period imprisoned alongside her mother. This experience catalyzes her rejection of crime. After their release, coinciding with Marius and Cosette's wedding, Azelma explicitly expresses a desire to live honestly, abandoning her father's path. She resolves to support her mother in reforming their lives, aiming to return to Montfermeil to run their former inn without Thénardier. This decision marks a departure from the original novel, where she accompanies her father to America as he becomes a slave trader.

Physically, Azelma has gray or green eyes and chestnut or auburn hair, often tied in a ponytail with a ribbon. She is depicted with a modest height of 145 cm, reflecting her youth. Her personality evolves from a compliant follower in childhood to a figure actively seeking redemption, shaped by familial influences and eventual self-determination.