She was a great-granddaughter of the Polish King Johan Sobieski as well as an exceptionally wealthy heiress. Because of the latter, King Louis XV of France took a personal interest in her marriage prospects and it was Jules Hercule Meriadec de Rohan, Duc de Montbazon, Prince de Guemene, who married her on 19 February 1743 when she was not yet seventeen. Two years later a son was born.
In November 1746 Louise contracted smallpox which, in those days, was often a fatal disease. During her convalescence, her family received a sympathy note from her first-cousin, Charles Edward Stuart, also known as 'the Young Pretender'. She recovered and, in August 1747, met and passionately fell in love with this first cousin who returned her feelings and they began an affaire.

In Louise's circles adultery was widely accepted so long as it was done discreetly. However, as neither Louise nor her husband had been unfaithful before, her mother-in-law kept a very strict eye on her as her husband was with the French army in Holland and her servants had been ordered, by her mother-in-law, to guard her virtue. Louise and Charles then resorted to secret midnight coach-rides; however, her mother-in-law had alerted the Paris police who reported what went on.

After a while, Louise found herself pregnant and resorted to sleeping with her returned husband to make him believe he was the father, but this enraged the jealous Charles into creating a scene.
Yet Louise's husband did nothing and gossip began to spread. In January 1748, confronted by her own father as well as her mother-in-law, Louise was forced to write to Charles ending their affaire. Nevertheless, Charles was still allowed to visit her and her family in order to refute the gossip about their affaire. In despair, Louise wrote more letters to Charles, threatening suicide if he didn't come to see her. He did so some three months later, again in a midnight assignation, but only to tell her he had a new mistress.
On 28 July 1748 a son was born and baptised Charles Godefroi Sophie Jules Marie de Rohan. It was her mother-in-law who wrote to Charles's father in Rome to tell of the news, but not that this child was the grandchild of the 'Old Pretender'. Having been accepted as a member of the Rohan family, several genealogical books mentioning the Rohans fail to mention this child.
Louise lived at least another thirty-three years and apparently was never unfaithful again. To all appearances she was a good wife and mother to her first-born but never had another child. She made occasional appearances at court, then later in life became religious and devoted much of her time to charity. When she died she, too, was buried in the convent des Feuillants together with her second child. However, there is uncertainty as to exactly when she died, either naturally in September 1781, or possibly, on the guillotine in 1793.
 

Source: Leo van de Pas