The title exists, but it is held by the Dukes of Norfolk and has been since 1660. This Duchess of Norfolk was named Charlotte Sophia Leveson-Gower. Her Wikipedia article, with this image, is here. A number of the Leveson-Gower Ladies were quite pretty.
Countess Charlotte Sophia wears dual sleeves - the inner one is quarter length and opaque while the outer one is full-length and made of sheer material.
Keywords: Lawrence, Charlotte Sophia Leveson-Gower, Leveson-Gower family, Fitzalan-Howard family, Duchess, British, straight coiffure, trapezoidal neckline, ruff, lace, modesty piece, vee décolletage, dual upper quarter length close sleeves, Empire waistline, necklace, cameo