María Francisca de Sales de Palafox Portocarrero y Kirkpatrick, "Paca," Duchess of Alba by Federico Madrazo y Kunz (private collection)
Empress Eugénie's sister wears a sumptuous dress in this portrait by Federico Madrazo y Kunz.
The Spanish site oronoz has an image that this is based on here.
Federico Madrazo is getting more press in the Anglophone world. He was a world-class portrait artist on a par with or better than Ingres. His English-language Wikipedia article is here. One place to find a compilation of his works is here.
Keywords: Paca Montijo, Duchess, Spanish, straight coiffure, floral headdress, veil, off shoulder vee neckline, modesty piece, cap sleeves, full skirt, flounces, lace, train, necklace, brooch, bracelets, order sash