They were married on 5 April 1894 but her dress says this photo could date from 1904. Her Hikipedia article is here.
Posted to the Royal Weddings Message Board by Chris on 1 April 2011; sepia tone removed by gogm.
Maria Isabella's sleeves are complex, even for an era of complex sleeves, and, if this is a wedding-related photo, her blouson bodice previews the next decade.
Keywords: Maria Isabella of Württemberg, Prinzessin Johann Georg, Princess Johann Georg, Duchess of Württemberg, Princess of Saxony, Württemberg family, Wettin family, Duchess, Princess, German, straight coiffure, high enclosing neckline, epaulettes, long accordion sleeves, engageantes, cuffs, blouson bodice, shallow-vee waistline, A-line skirt, pin, gloves