This is probably Geraldine Anson whose article in thepeerage is here.
From billinmn's photostream on flickr image cropped and crease in upper left corner and spots throughout image removed with Photoshop and sepia tone removed by gogm.
What to do with the wide hems of crinolines is a question facing designers. Some used Greek key patterns, others used various forms of stripes. This designer used a pair of multi-colored horizontal stripes joined by diagonal stripes of different material - all above a lace flounce.
Keywords: Geraldine Georgiana Mary Anson, Marchioness of Bristol, Anson family, Hervey family, Marquise, British, straight coiffure, hair ornament, high neckline, collar, long close sleeves, cuffs, ruffles, peplum, crinoline, flounces, lace, earrings, bracelets