Violet Lindsay Manners, Duchess of Rutland
Lady Violet Manners was one of a group of aristocratic politicians and intellectuals called "The Souls." This group included Margot Asquith, Diana Cooper, Emmeline Cust, Ettie Desborough, Alberta Windsor-Clive, and the Wyndham sisters.
From the Bain Collection of the USA Library of Congress. They give the date as 1910-1915 for this and many other images. Detail-enhanced by gogm; details of the dress are brought out at the expense of the background and chair.