Greta begins the series as an 11-year-old girl from a affluent family, celebrating her 12th birthday during the main storyline and appearing as a 16-year-old in the OVA special. Her initial demeanor exudes a polished arrogance, marked by boastful challenges and attempts to assert dominance through impromptu competitions. She fixates on a self-declared rivalry with Saga, relentlessly seeking validation through one-sided contests that others often dismiss. Beneath her showy exterior lies a growing vulnerability, particularly as her dynamic with Saga shifts from competitive clashes to an unexpected camaraderie. Persistent yet clumsy in her efforts to connect, Greta faces recurring comedic mishaps—embarrassing falls, botched schemes—that soften her edges without cruelty, charting her gradual emotional maturation.

The OVA glimpses her adolescent poise, hinting at quieter growth during the intervening years while maintaining her spirited core. Though her activities post-time-jump remain unspecified, her evolution reflects themes of shifting identities and the nuanced bridge between childhood rivalries and mutual respect. A discarded concept once proposed "Greta Grace" as her full name, though it never reached canonical use. Her arc balances humorous misadventures with understated sincerity, framing her journey as a blend of stubborn pride and earnest self-discovery.