Here it is - the actual Winterhalter portrait of Princess Alice dressed as a bridesmaid for her sister Victoria's 1858 wedding. The wedding took place on 25 January 1858 so the listed date is 1857.
From the lost gallery's photostream on flickr.
This portrait shows an early cage crinoline-era dress with a full dome skirt and vast expanses of white satin punctuated by colorful flowers.
Keywords: 1857, Winterhalter, Princess Alice, Hanover family, Hesse family, Romanov family, British, Princess, Grand Duchess, straight coiffure, floral headdress, veil, off shoulder vee neckline, modesty piece, bertha, lace, cap sleeves, engageantes, vee waistline, crinoline, flounces, floral bodice ornament, floral sleeve ornament, necklace, earrings, bracelets, gloves