According to this Wikipedia article, Saint Pol was a County in the Pas-de-Calais of northwestern France with the County seat at Saint Pol-sur-Ternoise. It was sold to the Duc de Joyeuse, Louis de Melun, in 1705. When he died, the Joyeuse title passed to Charles, Prince of Soubise who had two daughters by two of his three marriages. The first was Charlotte de Rohan and the second was Victoire de Rohan. This is probably Charlotte or Victoire de Rohan.
Used Photoshop to remove spots and flaws from the background.