We will start with the full name, Catherine Noele Grand de Talleyrand-Périgord, Princesse de Bénévent (b.1762). She started her life in a French colony in India and she was a total dish! She became Madame Grand after marrying a British Officer ("officers!!"), George Francis Grand. She soon found her self having an affair with another man, and things crumbled with her husband. She left and moved to London. She moved to Paris for 5 years or so, but at the dawn of the revolution she left for Britain again. (According to wiki she was selling it in Paris but I still cant find a published source on that!)
But then she met Charles Maurice de Talleyrand-Périgord, a French Diplomat, and he fell for her! Before long she was this dandy's mistress (well I don't know if he was an official dandy but I would say so!) Talleyrand had his own saucy history. He was a church man, as he could not be in the military due to a slight limp. He was also a total womanizer and was said to have fathered a handful of illigitiment kids including Eugéne Delacroix! (remember there were no Maurry shows called 'Whos Your Baby's Daddy?' back then). She became his live in love. He was not about to marry her, "Why buy the cow if you get the milk for free?" BUT after so many years, when Napoleon was around he was like 'okay thats enough you guys, marry, NOW'
So Catherine was married again, and just like last time it all fell apart. Soon she moved out and was living alone and Talleyrand paid for her to move back to London. She stayed there awhile, living comfortably but decided to move back to Paris! Afterall husband #2 was paying a fortune for her to live a luxe life. Le Sigh! She passed away in Paris, 1834. And that is the story of Madame Grand.