Nelly is a maid and servant of Mina Tepes, the vampire princess and ruler of the Bund. She is one of three personal maids who work alongside Nero and Nella. Nelly has medium-length black hair, hazel-green eyes, and red lips, and she typically wears a standard maid uniform. Her true form is a mouse, a trait that becomes relevant in a comedic subplot when Min Mei’s pet mouse becomes enamored with her.

Nelly is deeply devoted to Mina and serves her with unwavering loyalty. She is energetic and occasionally hot-headed, though she also displays a certain denseness, such as failing to notice a hole in her dress until it is pointed out. Her devotion to Mina fuels a strong dislike for Akira Kaburagi Regendorf, Mina’s werewolf protector and close confidant, because Nelly resents how much time Akira spends at Mina’s side. This animosity is one of her defining personality traits.

Within the story, Nelly functions as a supporting character who attends to Mina’s daily needs and helps maintain the household. Her role is primarily that of a devoted attendant, and she does not undergo significant personal development over the course of the series. Her interactions are largely confined to her fellow maids, Mina, and Akira, and her most notable moment involves her mouse form being used for lighthearted humor. Nelly has no exceptional combat abilities; her only supernatural trait is the ability to assume the shape of a mouse, which serves as her true form.