Maria serves as an active combatant in the Chasseurs, the Catholic Church's vampire-hunting faction, specifically within Unit Three under Sixth Paladin Roland Fortis. She stands as one of Roland's key subordinates, alongside Vice-Captain Georges. Her duties involve relentless pursuit of vampires through locations like the Parisian catacombs and direct confrontations with threats such as the Malnomen Predateur. Her appearance features closely cropped blonde hair, narrowed brown eyes, and freckles. She wears the standard Chasseur uniform: a black cloak and rosary beneath a larger white cloak fastened with buttoned straps, opting for distinctive buckled boots over the typical knee-high laced boots. She primarily wields a bow.

Maria possesses a reckless nature, frequently charging into perilous situations without hesitation. This impulsivity often results in injuries that worry her comrades, especially Roland. She harbors an intense, unwavering hatred for vampires, maintaining constant hostility and readiness to fight. However, she demonstrates fierce loyalty and concern for her fellow Chasseurs, exemplified when she protected Georges from an attack by pulling him to safety. This loyalty extends to Roland even when his actions contradict Church doctrines, such as forming alliances with vampires; Maria justifies her continued support as protecting Roland and humanity from vampire threats.

Her combat abilities center on expert archery, making her formidable at long range but less effective in close quarters. Like other Chasseurs, she utilizes performance-enhancing drugs to temporarily increase her speed, strength, and stamina during hunts.

Maria holds Roland in high regard, viewing him as excessively kind, particularly towards vampires. She shares a strong mutual dislike with Vanitas. While distrustful of all vampires, she exhibits slightly more tolerance towards Noé Archiviste compared to others. An additional skill noted in supplemental material is her exceptional cooking ability, which improved further after receiving praise from Roland.

She appears primarily during Unit Three's missions, including the Hunters of the Dark Arc in both the manga and corresponding anime episodes, participating in operations against central characters and supernatural entities.