Her brief Wikipedia article is here. She was neither infamous or noteworthy, a considerable departure from a long line of her predecessors. The New York Times article about her marriage is here.
From the USA Library of Congress Bain collection; I patched over several spots in the image including some on her face.
Eileen became Duchess of Sutherland in 1913, about the time a dress like this would be fashionable.
Keywords: Duchess of Sutherland - Eileen, Duchess, Sutherland family, British, bouffant coiffure, scoop neckline, necklace