Within the narrative of this anime, Gladys is the leader of a small but persistent group of would-be jewel thieves, frequently identified as the Grandis Gang. The trio, which includes her loyal but bumbling accomplices, are initially presented as comedic antagonists whose primary goal is to steal the mysterious Blue Water gem from the main protagonist, Nadia. Gladys is the clear head of this operation, displaying a sense of authority and determination that sets her apart from her often clumsy subordinates.

Her personality is a mix of theatrical vanity, frustration, and a surprisingly romantic core. While she projects an image of a sophisticated and cunning criminal, these moments of competence are frequently undercut by the failures of her plans, leading to comedic outbursts. Despite her initial villainous role, Gladys is not truly malicious; her character is driven more by a desire for treasure and status than by genuine evil. A crucial and defining aspect of her personality is her secret, deep-seated infatuation with Captain Nemo, the enigmatic commander of the submarine Nautilus. This unrequited love, bordering on an obsessive fantasy, becomes a significant comedic and dramatic trait, revealed in moments of solitude or inappropriate daydreaming.

Gladys acts as a persistent external threat that inadvertently pushes the main characters, Nadia and Jean, together and into further adventures. Her role in the story evolves over time, shifting from a straightforward pursuer to a more complex figure. At one point, she and her gang become stranded alongside the main protagonists, forcing an uneasy alliance. During this period of survival, her leadership skills and personal vulnerabilities are highlighted. The dynamic with her two crew members is a key part of her role, as they remain fiercely loyal to her despite her often harsh treatment of them. Her key relationships are therefore central to the plot: an antagonistic pursuit of Nadia, an unrequited romantic longing for Nemo, and a codependent, almost familial bond with her two companions.

Throughout the series, Gladys undergoes a notable development, transitioning from a purely antagonistic force to a more rounded and sympathetic secondary character. While her desire for the Blue Water may fade, her personal motivations, particularly her feelings for Nemo, come to the forefront, adding layers to her persona. Her abilities are not physical or technological, but rather lie in her organizational leadership and a flair for dramatic presentation. She is the one who devises the gang's plans and keeps her two larger, stronger, but less intelligent subordinates in line. While she possesses no special powers, her force of personality and persistent, if often unsuccessful, ambition make her a memorable part of the story.