From www.altesses.eu/princes030.php.
Beatrix wears an 1630s dress with wide lace collar and slashed sleeves showing a gold brocade material below.
Keywords: 1635, van Dyck, Beatrice Cusance, Cusance family, Lorraine family, Duchess, French, straight coiffure, square décolletage, lace collar, bertha, bows, over-dress, quarter length puffed over-sleeves, slashed sleeves, under-dress, puffed under-sleeves, necklace, earrings