This is a late medieval dress, the outermost garment being a surcoat with open sides to let the sleeves of rich material beneath show through. Wikipedia's article about 1400s dress includes this: "...Women's fashions of the fifteenth century consisted of a long gown, usually with sleeves, worn over a kirtle or undergown, with a linen chemise or smock worn next to the skin. The long-waisted silhouette of the previous period was replaced by a high-waisted style with fullness over the belly, often confined by a belt. The wide, shallow scooped neckline was replaced by a V-neck, often cut low enough to reveal the decorated front of the kirtle beneath..."
Keywords: Eleonore of Portugal, Empress, Habsburg family, straight long coiffure, high enclosing neckline, crown, fur, surcoat, waist band, natural waistline, long sleeves