From Wikimedia.
This may be an early portrait of Margherita Gonzaga. The fuzzy area at the top obscures part of her coiffure or headdress.
Keywords: Margherita Gonzaga, Margherita Gonzaga di Lorena, Marguerite de Gonzague, Marguerite de Mantoue, duchesse de Lorraine, Gonzaga family, Lorraine family, Duchess, high straight coiffure, tiara, hair jewelry, earrings, necklace, high neckline, lace neckline ruff, lace bertha, brooch, draped jeweled bodice ornament, jeweled sleeves