Her Wikipedia article is here. She did not marry, nor was she long-lived.
From the lost gallery's photostream on flickr.
The flared conformal ruff is a fashion note from around 1820. This one originates from the partlet-like section of Maria de Assunção's dress.
Keywords: Taunay, Maria de Assunção, Bragança family, Princess, Infanta, Portuguese, curly coiffure, floral headdress, partlet, high neckline, neck ruff, lace, bodice, square neckline, dual upper-puffed sleeves, Empire waistline, order sash, earrings