The artist is not identified where I can find this image, but the posing makes it look like a work by Gerrit van Honthorst.
From lisby1's photostream on flickr.
Princess Mary wears a hurluberlu coiffure and an opulent, but plain, dress and limited jewelry in keeping with Dutch tastes of the day. She looks like she is in her teens, dating this to 1647 - 1650.
Keywords: Princess Royal Mary Stewart, Stuart family, Orange family, Dutch, Princess Royal, hurluberlu coiffure, hair jewelry, straight neckline, bertha, elbow length puffed sleeves, basque waistline, full skirt, necklace, earrings, brooch