Her Wikipedia article is here.
Princess Antoinette wears a post-Empire dress, but with a waist band and puffed sleeves in this portrait from about 1820.
Keywords: 1820, Princess, German, hurluberlu coiffure, bandeau, off shoulder straight neckline, pleated bodice, puffed sleeves, waist band, Empire low waistline, close skirt, necklace, earrings