From Wikipedia.
Catherine wears the widow's attifet, but not a black dress in this Clouet portrait. Her bodice buttons up to her ruff.
Keywords: Clouet - François, Catherine de Medici, Medici family, Valois family, Queen, French, curly coiffure, attifet, veil, high enclosing neckline, ruff, buttons, rolled sleeves, earrings, rolled sleeves