What makes this outfit show formal balance is that the outfit has a mirror image of both sides. The elements of design that are present in this picture that help create balnce is that at the top part of her shirt, there are two flaps that come down that are identical and mirror each other. Also the skirt is the same all around.
Airplane chic...“So be sure when you step, Step with care and great tact. And remember that life's A Great Balancing Act. And will you succeed? Yes! You will, indeed! (98 and ¾ percent guaranteed) Kid, you'll move mountains.” ― Dr. Seuss, Oh, The Places You'll Go!