Madame du Barry was not born a noble. She used to be a prostitute, orphaned at age five, she prostituted herself to survive. However, she was sick of her life and wanted a better one, even if it meant doing horrible things to get what she wants. She blackmailed one of her rich customers to give her a large ounce of money. Soon she caught the eye of the late Count du Barry and they married and she became countess du Barry, but she kills him the next day with poisoned wine and takes over his fortune and becomes the mistress of King Louis XV. Because of her relationship with Louis, the women swoon over her as if she was the queen of Versailles.
The aunts of the late queen despise her because of her profession as a prostitute and the things she did to get into Versailles and gaining power. When Marie Antoinette becomes princess of France, she see's Madame du Barry and had a bad feeling about her and already saw her as a vulgar woman, when the aunts tell Marie Antoinette about Madame du Barry, Marie Antoinette was disgusted and decided she would ignore Madame du Barry as she does not want people to think it's acceptable to let whore's into a distinguish place such as Versailles.
Maria Theresa of Austria, queen of Austria and mother of Marie Antoinette, worries that her daughter rejecting Madame du Barry might cause problems for her in Versailles but understands why her daughter does this as she herself would whip such women and throw them into institutions and even she finds Madame du Barry horrible. Not wanting a war to happen between France and Austria, she sends her advisor, Comte de Mercy, to France. Mercy advises the princess to make peace with Du Barry, but Marie Antoinette does not obey the warnings as she wants to make it clear that women like Madame du Barry can not be allowed in Versailles until King Louis XV shows his displeasure with her attitude towards the countess. Marie Antoinette finally speaks to Du Barry. Months later, King Louis XV gets smallpox. Before dying, the bishop, hearing Louis's confession, and orders the removal of the King's sin, which is none other than, Madame Du Barry. King Louis XV dies and Du Barry is taken to a covent, where she remains until 1793, the year in which she is guillotined for her crimes in murdering her late husband and her other crimes in Versailles that Louis XV let her get away with.
Despite her cruel tactics and spiteful nature, she shows her soft side to Oscar as she helps her leave Versailles as she told her her story of her hard childhood. She tells Oscar that everything she did was to survive and be able to have a good life since France is in utter dismay, which Oscar realizes when she met Rosalie who offered her body so she can get money to feed herself and her mother. Madame du Barry's experience is what made Oscar begin to realize how corrupt nobility and the clergy were.