From Wikimedia.
María Ignacia wears a unique dress with a basque waistline set off with a frilly peplum and a (not off shoulder) scoop neckline framed by a double bertha while her skirt and over-skirt are not supported.
Keywords: 1776, Esteve, María Ignacia Countess of Altamira, Álvarez de Toledo y Gonzaga family, de Moscoso y Alvarez de Toledo family, Countess, Spanish, long curly coiffure, chemise, scoop neckline, lace, bodice, scoop décolletage, bows, bertha, elbow length full sleeves, engageantes, peplum, basque waistline, full skirt, over-skirt, flounces