Oscar's relationship with her soldiers in the French Guards. At first they resent her for the relentless drills, her gender and coming from the Gards du Corp, but with time they grow to adore her, and at one point they refuse orders from colonel De Vouillet (the regimental commander) because Oscar (who had been arrested for refusing said orders as immoral) wasn't there to give them. Also, when Oscar mutinies to join the rebellion of Paris the entire rank and file of the company join her, and the officers, who remained loyal to the crown, apologize for not joining her and take their time to return to Versailles and inform the command about the mutiny.
Also, her relation with the soldier of the Garde du Corps: when the Garde du Corps company under Girodelle's command (the same that Oscar had commanded before taking control of the whole regiment and then transferring to the French Guards) is sent to disperd the National Assembly (the same orders that Oscar had refused), the soldiers are ready to attack the delegates, including nobles like the Marquis de Lafayette, but immediately return to their barracks when Oscar orders them back.
When Marie Antoinette finds out Louis has been told that their son is supposedly the son of Fersen, she, sad, offers to kick her beloved Fersen out of the court to quell the rumours. Louis reply? To not do it, for three reasons: because Fersen was a loyal and true friend; because he knew that Marie Antoinette loved him, and thus needed him; and because he also knew Marie Antoinette and Fersen had never allowed themselves to cross the line from platonic love to carnal love because she was the Queen of France.