Thank you wuvums for providing the correct name for this lady and lifespan dates that can be used to approximately date this portrait! (Input provided on 8 November 2008 when the next image was posted on Webshots.) This image of Eleonora di Garzia di Toledo, who was raised by Eleonore de Toledo, wearing a dress showing Spanish influence is often called Maria de Medici. Her Wikipedia article is here.
The Wikipedia article for Alessandro Allori is here.
Upgrade image from Wikimedia posted on 3 February 2015.
Her bodice fastens with small gold buttons and loops. A double row of rolled loops trims each shoulder. The material of her sleeves matches the material of her under-skirt. The image, including the face, resembles a portrait of Laura Martinozzi, a niece of Cardinal Mazarin brought by him to France to secure a good marriage.
Keywords: 1570, Allori, curly coiffure, jeweled ribbon headdress, vee neckline, neckline ruff, modesty piece, rolled sleeves, long tapered false sleeves, cuffs, girdle, vee waistline, full skirt, under-skirt, necklace, carcanet necklace, earrings, jeweled ruff, gloves