Purple/plum dress

Purple/plum dress. Bought from another posher, but is way too big. Brand is Merona. Sz says 4, but this is a big4 (have no idea wht's up with tht), feels at least a sz and a hlf or een 2 sizes smaller. waist: 15", hip: 18.5", bust: 15.5", length: 37". Design is meant to draw in the middle.