The first paragraph of her Wikipedia article is, "Doña Ana de Mendoza y de la Cerda, Princess of Eboli, Duchess of Pastrana, (in full, Spanish: Doña Ana de Mendoza y de la Cerda ), (29 June 1540 – 2 February 1592) was a Spanish aristocrat, suo jure 2nd Princess of Mélito, 2nd Duchess of Francavilla and 3rd Countess of Aliano. She was considered one of Spain's greatest beauties, despite having lost an eye in a mock duel with a page when she was young." She had 10 children and spent her last years in prison for leaking state secrets.
This may not be a portrait of her from her era. From the lost gallery's photostream on flickr. Extensice spotting of her neckline removed with Photoshop by gogm.