Sarah Frances Russell, Lynn’s elder half-sister, is the daughter of George Russell and his first wife Frances, whose death left Sarah motherless from infancy. Her sole inheritances—her mother’s flute and musical score—anchor her identity as a flutist and painter, while shaping her guarded demeanor. Initially cold toward Lynn, her aloofness stems from shared maternal loss and unresolved grief, though she gradually becomes the younger sister’s protector, confronting the abusive Wibburys/Waverleys. Chronic illness, loneliness, and her father’s absences deepen her emotional reserve, yet she evolves into a figure of compassion, openly comforting Lynn and defending her innocence—a transition more pronounced in anime adaptations, which soften her initially sharper manga portrayal.

Her narrative centers on a quiet, mutual romance with childhood friend Arthur Brighton, culminating in marriage—a stabilizing contrast to Lynn’s fraught relationship with Arthur’s brother Edward. After financial ruin costs the family Marble Mansion, Sarah moves to Woburn Castle, her bond with Lynn preserved through matching heart-shaped lockets bearing family portraits and inscriptions of mercy, courage, and nobility. The flute serves both as emotional refuge and a conduit to her grandfather.

Inheriting her mother’s straight blonde hair and icy blue eyes, Sarah’s appearance highlights divergent maternal lineages, positioning her as a bridge between the Russell family’s history and present. Her arc concludes with her embracing the societal ideal of a Proper Lady, mirroring Frances’ legacy, yet asserting autonomy through choices like marrying for love rather than duty.