Herzogin Marie José in Bayern, Duchess in Bavaria née Princess of Portugal by ?
Her Wikipedia article is here.
From Miss Mertens' photostream on flickr.
This dress is bound to be noticed with its bold diagonal stripes and tall triangular lace appliqué decorations.
Keywords: Marie José of Bavaria, Bragança family, Wittelsbach family, Princess, Duchess, German, straight coiffure, knotted coiffure, collar, lace, long tight leg-o-mutton sleeves, close skirt, train