Cosette, like Valjean, grows up in an atmosphere of poverty and fear, but she is rescued from this life before her innocence gives way to cynicism. Though she spends a number of years under the tyrannical care of the Thénardiers, she never adopts their cruel views, which indicates that she possesses a fundamental decency and goodness that they lack. Once Valjean takes charge of Cosette’s upbringing, she quickly transforms from a dirty, unhappy child into a lovely, well-educated young woman. For Hugo, this transformation is so natural that he does not even bother to walk us through it and instead skips several years ahead.
Though she is obedient and fiercely loyal to her adoptive father, Cosette also has her own personality, which emerges as she enters adolescence and begins to hunger for a less sheltered life. In this period of their lives, Valjean’s role temporarily changes from Cosette’s savior to her jailer. Cosette’s ability to truly love Marius, however, is due in large part to Valjean, who has taught her to trust and love. In the end, Cosette remains true to her upbringing, and her love for Marius becomes her way of applying to her own life what she has learned from Valjean.