She visited Louis XV when he was with his army at Dunkerque and again in Metz. When Marie Anne visited the king in Metz near the front she was accompanied by Diane Adélaïde. Besides being an amiable companion, Marie Anne did not consider her simple sister much of a rival.Herman, Eleanor (2005). Sex With Kings p. 116 It was rumoured at the time that one of the methods by which Marie Anne kept the interest of the king was to periodically offer him a ménage à trois with her sister, Diane Adélaïde de Lauraguais. That Lauraguais actually began sleeping with the king at this point is debatable. Nevertheless, the widespread rumors made the two sisters' visit to the king in Metz a national scandal. During the notorious visit of the sisters in Metz, the king suddenly fell gravely ill on 8 August. Fearing to be at his deathbed, Louis XV was afflicted by a religious crisis and wished to renounce his adultery and mistresses and ask his wife for her forgiveness. The queen was called to Metz, and Marie Anne and Diane Adélaïde ordered to leave. During their journey back to Paris the sisters were taunted by mobs who threatened to lynch them and their coach was attacked with stones.
