Her Wikipedia article is here.
From eBay; sepia tone removed and circular crease in lower left, spots, and right edge fixed with Photoshop by gogm.
Marie's dress is late pre-war (or maybe early 20s?) style with a tight skirt with simple line and materials. Her dress may have an over hanging bodice, faintly visible above her arm.
Keywords: Augusta Victoria Hohenzollern Bragança, Hohenzollern family, Bragança family, Princess, Queen, curly coiffure, elbow length close sleeves, cuffs, no waistline, over hanging bodice, tight skirt, necklace, earrings