Casanova's Henrietteʔ
It is speculated that she was Adélaide de Gueidan. This is her in a painting "Adélaïde de Gueidan et sa sœur au clavecin" ("Adelaide de Gueidan and her Younger Sister on Cembalo" (harpsichord) by Claude Arnulphy, circa 1735-40. I have also seen it attributed (wrongly?) to Nicolas de Largillière.