From Wikimedia. Also posted to her new Subalbum.
Lady Dufferin appears to be wearing a fur-trimmed coat over an evening dress, perhaps with a beaded bodice.
Keywords: 1891, R. Taylor & Co., Hariot Georgina Rowan-Hamilton, Hariot Georgina Hamilton-Temple-Blackwood, Marchioness of Dufferin and Ava, Baroness Dufferin and Clandeboye, Lady Dufferin, Countess of Dufferin, Rowan-Hamilton family, Hamilton-Temple-Blackwood family, Marquise, British, curly coiffure, hair jewelry, earrings, necklace, jeweled crucifix, fur-trimmed coat, lace-trimmed lapels, bodice, trapezoidal neckline, fitted bodice, sweetheart neckline, strap sleeves, vee waistline, over-bodice, bertha, elbow length over-sleeves, bracelets, order sash order star, order bows, close skirt