Since 1727, the position of royal governess had been held by some female member of Madame de Marsan's family. Her great-grandmother, Madame de Ventadour, was the governess of the children of Louis de France, Duke of Burgundy, including Louis XV, and then the children of Louis XV himself. In 1735, Ventadour resigned and the post went to Madame de Marsan's aunt, Marie Isabelle de Rohan, Duchess of Tallard. When Madame de Tallard died in 1754, Marie Louise was appointed to her aunt's position as royal governess and took over the care of Louis XV's ten children. Madame de Marsan remained as governess for twenty-two years, and taught the future Louis XVI and his siblings. Her favorite charge was the Count of Provence; he in turn called her ma chère petite chère amie. She took a progressive initiative when engaging the Marquise de la Ferté Imbault, daughter of Madame Geoffrin, to educate the princesses in philosophy, a subject normally only taught to boys at that time. In practice, she turned the education of Elisabeth of France over to the sub governess Marie Angélique de Mackau, but Clothilde of France was her favorite among her female pupils, and she accompanied her on her journey to her wedding in Savoy in 1775. During her tenure as royal governess, she was granted an apartment in the Tuileries Palace, which was called :fr:Pavillon de Marsan|Pavillon de Marsan after her. She was commonly known as Madame de Marsan. She had an influential position at court, where she was a powerful force within of the Dévots and a guardian of the privileges of her family. Reportedly, Madame de Marsan disliked the marriage between the future Louis XVI and Marie Antoinette of Austria in 1770; she would have preferred another match for the Dauphin, and continued to belong to the opposition of Marie Antoinette after her arrival to France. In 1776, she resigned from her position during an mass exodus of older nobles from the court because of Queen Marie Antoinette's disdain for formal court etiquette. She resigned her post in favour of her niece, the Princess of Guéméné. She resided at her hôtel on the rue Neuve Saint Augustine in Paris.
Later life
In 1777, Marie Louise used her influence with King Louis XVI to have her cousin Louis René de Rohan appointed the Grand Almoner of France. In 1785, she unsuccessfully appealed on her knees to the queen, despite her dislike for the latter, to show mercy to her nephew the cardinal de Rohan, who was implicated in the famous Affair of the Diamond Necklace. She appeared in court during the case against Louis de Rohan alongside the rest of the Rohan clan, dressed in black, and when the judges arrived, she reportedly rose and proclaimed: "Messieurs, you have come to judge us all!" She emigrated from France in 1789 after the beginning of the French Revolution. She died in Regensburg in exile at the age of 83.