Lady Emilie de Jarjayes, Oscar's mother and the second wife of General de Jarjayes. In the series she is the lady in waiting of Marie Antoinette.
In the prequel to Rose of Versailles, when she was a young woman named Georgette, she was betrothed to a man old enough to be her father. But then she met Francois de Jarjayes, a young widow with no children, they fell in love and consummated their relationship, but felt ashamed that she broke her agreement to the arrange marriage the other man. She confessed to her mother of what she did, but her mother was understanding and she called off the betrothal. She and Francois were able to marry when it was revealed that Georgette's great-grandfather, Georges de la Tour, was a Painter of the King for Louis XIII, and therefore there'd be no need to elope.
Oscar is fiercely protective of her mother, as shown when Oscar finds out by the king's orders that Madame du Barry wants her mother as her lady in waiting to get Oscar on her side when she and Marie Antoinette were in a feud. Eventually she becomes Marie Antoinette's lady in waiting by Oscar's consent to Marie Antoinette so Madame du Barry can't get to her, but when Madame du Barry tries to frame Madame de Jarjayes for the death of a maid from poisoned wine supplied by Madame du Barry, Oscar catches her and defends her mother from the woman.
When Oscar was born she was still resting from giving birth, but her older daughters and Nanny were horrified when their father and master declared he will raise Oscar as a boy and make her the heir to the Jarjayes military legacy as there were consequences for such a choice as Oscar's life would be in danger constantly from protecting the queen from her enemies, and the fact she can never truly live as a woman, despite the privilege of being free in a man's world while women were not allowed.
While Emilie loves her husband, it can be assumed that she was against her husband raising their youngest daughter as a boy and how he is sometimes physically abusive and harsh towards Oscar. In the manga, Oscar see's her mother and cries how she is not her father's doll and her mother comforts her and tells her to follow her heart and that Oscar is who she is regardless of her gender and that her father can never change that. She is also shown to be supportive of her daughter doing feminine things, like wearing a dress for a ball or embracing her feelings for Andre.
According to history, when the Revolution began and Marie Antoinette and her husband tried to escape from house arrest, her husband escape France to Italy and he and Emilie got divorced for convenience to protect Emilie from being executed due to her husband being loyal to the royal family up until Marie Antoinette's death and got remarried in 1797.
She died in 1837. Her death year is changed in a side story about Fersen and Marie Therese. In the story, General de Jarjayes admits that she died in 1790 from sorrow as Oscar and Andre died the year before in the Battle of Bastile.