According to her brief Wikipedia article, she was the first of three wives of Alfonso d'Este.
Upgrade image posted 5 October 2013 from the museum's Web site; some small spots in the background and the upper and left edges fixed with Photoshop by gogm.
Lucrezia de Medici wears a somber black dress with French sleeves and a wide flared collar surrounding her ruff that is decorated with four tassels on each side in this 1560 Bronzino.
Keywords: 1560, Bronzino, Lucrezia de Medici (1545-1561), Medici family, Este family, Duchess, Italian, jeweled headdress, high neckline, collar, ruff, tassels, chemise, modesty piece, slashing, French sleeves, slashed sleeves, cuffs, girdle, vee waistline, Spanish farthingale, earrings, brooch, jeweled pendant chain