The Red-haired Witch is the younger incarnation of Charlotte, Mary's great-aunt. As a student at Endor College, she possessed distinctive red hair and demonstrated exceptional magical aptitude, earning recognition for her talents. She discovered the rare and powerful fly-by-night flowers growing on the campus grounds. This discovery drew the intense interest of her instructors, Madam Mumblechook and Doctor Dee, who became obsessed with harnessing the flower's properties. They pursued dangerous experiments aimed at transforming ordinary humans into witches.

After witnessing the catastrophic failure of one such experiment, which horrifically transformed a fellow student, she recognized the grave risks and ethical violations inherent in continuing this research. To prevent further misuse, she resolved to steal the fly-by-night seeds and flee Endor College. Her escape triggered a destructive laboratory explosion that caused Doctor Dee to lose his arm. Following this event, she vanished from Endor, discarding her broomstick and severing all ties to the magical world. She chose to live an ordinary, magic-free life thereafter.

Years later, her legacy resurfaces when Mary discovers her hidden cottage on a remote, sentient island. Inside, Mary finds spellbooks, research notes, and a communication mirror—all remnants of the witch's past. Through these artifacts, the Red-haired Witch guides Mary, revealing her history and the truth about Endor's experiments. She explicitly warns Mary against the corrupting influence of magic and urges her to abandon the remaining fly-by-night bulbs. Despite this caution, her experiences and resolve empower Mary to confront Endor's corrupted leadership and dismantle their operations.