My own take of Mademoiselle Relda from original book series of The Great Mouse Detective; "Basil of Baker Street". She was known to be based on Irene Adler as Basil from Sherlock Holmes, but unlike Sherlock Holmes series, Relda is Basil's love interest. So, I have made some head canons for my version of Mademoiselle Relda.

Relda Eclair is French-American mouse lady, her parents moved to London, England. However, the huge inequality of rich and poverty taking place in Victorian England cost her family fortune and her parents' lives, leaving little Relda orphaned. Fortunately, three of compassionate rat ladies of Cabaret theater took her in and raise her as their own. As Relda grows, she found her talents in acting, dancing and singing as she was scouted to attend proper lessons before her debut as Opera actress. However, not everyone welcomed her in the theatre; some of the jealous actresses attempted to sabotage her or even harming her to prevent her fame from growing. Yet, Relda was no fool. Witnessing from her childhood as an orphan, in Cabaret club, and so on, she used her intelligence and wits to thwart the jealous actresses' schemes and have them fired for good.

Being raised by three rat Cabaret ladies who told her to be smart to survive, Relda used her charm and talents to attract wealthy audience into investing her theatre. There, she met one of them, the Grand Duke of Maldonia, and she decided to put her skills on him hoping to gain worldwide connections for her innate passion in social adventures. She usually strips off obnoxious, wealthy men's fortune for selfless act, anyhow. Especially, to feed the orphans or offering jobs to the impoverished parents for their children. Of course, she kept this as a secret. Behind her femme fatale persona, she has a nurturing nature towards the little ones (even visiting her caretakers to spend time with them and some of their children).

Her life changes when she encountered Basil of Baker Street who have learned of her reputation among the noblemen as "the Circe of London" as he was requested by the Grand Duke of Maldonia to retrieve anything she'd use to threaten him since he'd be married to the princess Tilde of Dunbroch. However, Basil has underestimated the Prima Donna who have outwitted him twice (one from setting trap in her house, the second by winning the chess for the winner can take the photography of her and the Grand Duke). The detective mouse's pride damaged at first, but learns that she knew he'd come for the photography by the Grand Duke and simply gave it to Basil, stating it is up for his decision to judge this affair. Basil responded by ripping it in half and burning the side of the Grand Duke was taken, keeping her side of photograph and stated the case is closed. However, in an exchange, he would visit her occasionally whenever he needs further information on the cases he'd determine to be solved ASAP. Relda agreed, but also added that she won't unconditionally help him as he'd need to pay by playing chess match with her. Enraptured, Basil accepted.