According to her Wikipedia article, she was the niece of Mme. de Montespan and Marie-Anne de La Trémoille. She had a brief fling with Louis XIV in 1665 when she was around the age of 14. Her family had her married off to Marquis Michel Sublet d'Heudicourt. She later made the mistake of revealing Louis XIV had fathered children by Madame de Montespan causing her to be banished from court in 1672. Fortunately for her, Mme. de Maintenon supported her so she was allowed to return in 1677.
Her French-language Wikipedia article is here.