Personally my favorite SG costume is the Superman The Animated Series white tanktop and gloves, but I admit that one only really screams 'super' when it's assisted by the visual aide of her slowing the fall of a jetliner or something. This version is more immediately striking as a cosplay.
Fantastic Supergirl cosplay!!! The costume looks really cool and faithful to the comics. I love the photo- it has an epic quality to it. I love how the cape is flowing in the air! Lovely smile and totally heroic pose as well!