Jeanne de Vallois, also referred to as Jeanne de la Motte, appears in The Rose of Versailles as a central antagonist whose schemes have significant repercussions for the entire court of Versailles. Her character is based closely on the historical figure Jeanne de Valois-Saint-Rémy, a French con artist and the primary instigator of the Affair of the Diamond Necklace. In the story, she is known for her cunning intelligence, relentless ambition, and striking beauty, which she uses as a tool for manipulation. Driven by a deep resentment of her impoverished noble lineage and a burning desire to reclaim the wealth and status she believes is her birthright, she stops at nothing to climb the social ladder.

Jeanne and her husband, Nicolas de la Motte, orchestrate the elaborate fraud of the diamond necklace to enrich themselves. She recruits a woman named Nicole d'Oliva, a prostitute who bears a remarkable resemblance to Queen Marie Antoinette, to impersonate the queen in secret meetings with the Cardinal de Rohan. This deception convinces the Cardinal that he has regained the queen's favor, leading him to act as the intermediary to purchase an incredibly expensive diamond necklace on her behalf, a necklace he then hands over to Jeanne.

Her role in the story is to act as a catalyst that accelerates the French populace's disillusionment with the monarchy. After her arrest for the crime, Jeanne does not go quietly. During her trial, she launches a series of spectacular and false accusations against Marie Antoinette. She claims that the queen was the true mastermind of the necklace plot and goes further to suggest that the queen engaged in intimate relationships with women, specifically naming the Duchess de Polignac and even Oscar François de Jarjayes as her lovers. These scandalous lies are eagerly embraced by a public already primed to despise the Austrian-born queen, branding Marie Antoinette as "L'Autrichienne" and a symbol of depraved aristocratic excess. This public relations disaster deals a severe blow to the already tarnished image of the royal family.

Her key relationships are defined by exploitation. She uses her husband Nicolas as a co-conspirator, while figures like the Cardinal de Rohan are merely pawns in her game. She also maintains a connection to Rosalie Lamorlière, whom she does not initially know is her half-sister. Following her conviction, she is imprisoned and branded with a "V" for voleuse (thief) on her shoulders, but she manages to escape. Once free, she continues her campaign of vengeance from exile, writing and publishing scandalous memoirs filled with further invented erotic stories about the queen and her circle. These pamphlets become enormously popular with the common people, further inciting revolutionary fervor. Her character development shows a descent into ever more desperate and reckless behavior. Ultimately, cornered and facing capture, her story concludes in a final act of destruction, dying in a fire set during a chaotic confrontation. In some versions of the story, she also tries to use her sister Rosalie to her advantage, threatening to expose her connection to Oscar if Rosalie does not comply with her demands. Her notable abilities lie not in physical combat but in psychological warfare; she is a master manipulator, a convincing liar, and a woman who weaponizes her charm and perceived victimhood to destroy those she holds responsible for her misfortunes.