Although her family was Burgundian (i.e., supporters of the Duke of Burgundy), in early 1407 the seventeen-year-old Odette became the mistress of King Charles VI after the death of his brother Louis I, Duke of Orléans, Burgundy's rival.
Queen Isabeau, the victim of beatings and abuse from her violent, schizophrenic husband, allowed Odette to substitute for her without difficulty. Isabeau feared and loathed the king. By some accounts, she herself arranged for Odette to take her place in the mentally ill king's bed; by others it is believed that Duke John the Fearless offered the young Odette to the King, in order to ensure the influence of the Burgundian party. Odette and Charles VI had only one daughter together, called Marguerite, who was born by the end of 1407.
Called la petite reine — "the little queen" — by Charles's court, Odette was described as a lively, beautiful young woman with a gentle disposition. Apparently she loved and cared for her unhappy sovereign with the utmost patience and devotion. She is credited with introducing playing cards into France, "for the amusement of [Charles VI] during his paroxysms of insanity."
According to some authors, Odette wore the clothes of the Queen in the royal bed each night, and Charles didn't notice the substitution. Honoré de Balzac refers to her selflessness in one of his earlier novels, La Dernière fée:
"So Abel was like the King Charles VI, that the little queen Odette de Champdivers consoled him while his Queen Isabeau danced with the Duke of Orléans in the palace where her husband was suffering".
During the almost fifteen years of their relationship, the King gave Odette rich gifts as a reward for her dedication to him; she also received two fine manors in Créteil and Bagnolet (the latter probably located in Malassis), and the estate of Belleville in Poitou.
Odette was at the King's side on his deathbed (21 October 1422); it is said that the last words of Charles VI were her name: "Odette, Odette". Queen Isabeau was absent from her husband's funeral.