After seeing the original at the Royal Collection Web site; it appears this is a print based on the original prepared by Winterhalter for Queen Victoria.
From teatimeatwinterpalace.tumblr.com/page/5; sepia tone removed by gogm.
Princess Louise is portrayed wearing a middle 1860s crinoline evening dress with an off-shoulder neckline, small ruffled trim, quarter length sleeves, and crinoline.
Keywords: 1865, Winterhalter, Princess Louise, Princess, Hanover family, Sutherland family, British, straight coiffure, curly chignon, off shoulder neckline, modesty piece, ruffles, quarter length close sleeves, vee waistline, crinoline, necklace, earrings, bracelets