I cannot find anything about her other than this portrait.
From Wikimedia; veiling reflections in upper right corner reduced with Photoshop. Also posted to the Revolutionary, Napoléonic, and Romantic Era Album.
Her under-skirt is made of luxurious material, but not the over-dress, and she wears no jewelry.
Keywords: 1799, Hetsch, Elisabeth Christiane, Freifrau von Bouwinghausen, Baroness, German, curly coiffure, ribbon headdress, bodice, vee décolletage, sheer bertha, close over-skirt, wrap, tassels