She married Alfonso I d'Este, Duke of Ferrara, after the death of his first wife, Lucrezia Borgia. She had been Alfonso's mistress before Lucrezia's death in childbirth; Lucrezia was also unfaithful. Her terse Wikipedia article is here.
From www.everypainterpaintshimself.com/galleries/; spots throughout image, but especially in the background removed with Photoshop by gogm. The background was then blurred with Photoshop by gogm. The background is, therefore, heavily altered.
Laura de Dianti's dress has a somewhat high waistline and a décolleté square neckline partially filled in by her white camica (chemise). She uses a gold-banded sash to conceal her cleavage. Her puffed virago sleeves and white under-sleeves could be fashionable 100 or more years later. Her headdress, placed behind a jewel star, could be made from the same cloth as her sash.
Keywords: 1523, Titian, Laura de Dianti, de Dianti family, Este family, Duchess, Italian, long straight coiffure, hair jewelry, headdress, chemise, sash, scoop neckline, over-bodice, square décolletage, three quarter length puffed virago sleeves, arm bands, long full under-sleeves, cuffs, natural high waistline, full skirt, earrings, rings