This particular Maria Josepha was daughter of Empress Maria Theresia and Emperor Franz I. She died of smallpox at the age of 16. Her Wikipedia article is here.
Maria Josepha wears a dress adorned with gold and lace in this Mengs portrait from around 1765.
Keywords: 1765, Mengs, Archduchess Maria Josepha, Archduchess, Queen, Habsburg family, straight coiffure, jeweled headdress, scoop neckline, bertha, lace, bows, stomacher, elbow length close sleeves, back-forward flared engageantes, vee waistline, panniers, train, jeweled neck band, earrings, fan, mantua