Tabitha, born Charlotte de Gallia, is the daughter of Duke Charles, younger brother to King Joseph of Gallia. After her father died in a succession conflict, Joseph claimed the throne. During a royal event, her mother consumed poisoned wine meant for Charlotte, losing her sanity and thereafter mistaking a doll named Tabitha for her daughter. Charlotte adopted the name Tabitha to stay close to her mother.

King Joseph forced Tabitha into lethal missions—slaying monsters and retrieving artifacts—hoping she would perish. Surviving these earned her knighthood, though Joseph blocked further advancement. At Tristain Academy of Magic, she maintained a quiet, stoic presence, often reading alone. She wielded a curved staff for wind-water hybrid magic and formed a silent but close bond with Kirche von Zerbst. Her familiar, the blue wind rhyme dragon Sylphid, remained her loyal companion, capable of human transformation as Illococoo.

Blackmailed by Joseph, Tabitha aided the antagonist Sheffield in capturing Louise Vallière, confronting Saito Hiraga. Her failure resulted in revoked knighthood and kidnapping by Joseph’s agent, the elf Bidalsha. Imprisoned in Gallia and facing forced dosing with the same mind-altering poison that afflicted her mother, she reflected on betraying Saito, believing reconciliation lost. Saito and allies rescued her before the potion took effect. This triggered a profound emotional shift: Tabitha wept openly—a rare vulnerability—and vowed to protect Saito as repayment. Her magic advanced to Square-class during the clash with Bidalsha.

After Joseph’s death, Tabitha restored her mother’s sanity using a curative potion and ascended the Gallian throne as Charlotte de Gallia. Her reign was complicated by the emergence of her twin sister, Josette—secretly sent to a monastery at birth due to Gallian traditions demanding one twin’s death. Manipulated by Romalia and the priest Julio, Josette usurped the throne. Following Romalia’s exposure, Tabitha abdicated to Josette and moved into Saito’s residence. Her relationship with Saito evolved, culminating in a strategic kiss to reignite Louise’s void magic during battle—an act acknowledging Saito as her childhood story’s rescuer figure, "Ivaldi." She occasionally displayed affectionate gestures toward Saito, signaling a departure from her former reserve.

Her narrative extends into spin-off light novels (*Zero no Tsukaima Side Story: Adventures of Tabitha*), detailing her knightly missions in Gallia.