She and Rosalie loved each other, but when Jeanne was starting to reach her goal to become a noble and her lust for her lavish lifestyle grew, she saw that Rosalie, thanks to Oscar, had free access to Versailles, and she was afraid that Rosalie would expose her and would lose everything, so she was determined to make sure Rosalie never tell anyone by ignoring her, even going as far as to send her husband to kill Rosalie.
While she gained pity from Marie Antoinette, the money she gave Jeanne, according to her, was not enough for her lifestyle. Finally at her breaking point, Jeanne decides that she actually wants to become queen of France and plotted to frame Marie Antoinette, when she finds out about the diamond necklace that the late king was making for Madame du Barry was finally finished, that's when she devised a plot that would become the most famous crime in French history, the Affair of the Diamond Necklace
When she was caught, she was taken into France's criminal court where she stood trial. At first she was denying everything, but when the judge brought in Nicole d'Olivia, a blind prostitute who she hired to impersonate Marie Antoinette in the crime, she tells the truth and Jeanne had no choice but confess. However, she still lied about Marie Antoinette being involved and said she and Marie were lesbian lovers who conspired the plot together, and that part ruined Marie's Antoinette's reputation even more.
Before being sent to jail, she was marked with a hot iron that had a symbol on it meaning "Thief", and since then people have been supporting Jeanne, begging for her release and the public went against Marie Antoinette. Soon she escapes and when her failed attempt to kill Oscar is about to kill her, she kills her devoted husband Nicolas, the one person in the world (except Rosalie) who is still on her side, because she does not wish to die alone and knew Nicholas couldn't live without her and did not want her husband to be put in prison and executed for her crimes, showing her deep love for Nicholas after years of using him.Nicholas happily accepted his death as he would go wherever Jeanne is, Jeanne was happy when he said that, the two share a passionate kiss before their death.
Despite Jeanne's selfish actions, she still had a few tenderspots in her heart, when she intended to kill Nicole d'Olivia to not have a witness to confess, she was unable to bring herself to do it. Apart from Nicole and Rosalie, Jeanne treated no one else like a human being. And she has a deep love for her husband, despite the abuse she put him through, She is a highly fictionalized Jean de Valois Saint Remy ￼, the mastermind behind the infamous Affair of the Diamond Necklace.￼