From pinterest.com/annabelmallia/princess-charlotte/.jpg.
This is the dress worn by Princess Charlotte for the Dawe portrait seen in the last image, color faded by time. The chemise is different and the neckline in the portrait could be called a W-neckline.
Keywords: 1817, Princess Charlotte of Wales, Welf family, Wettin family, Princess, British, chemise, modesty piece, long full sleeves, bodice, U-neckline, strap sleeves, waist band, Empire waistline, maxi-length close skirt