If I can recommend a few things, one would be to push the "V" shape you have all around the design. Right now the left leg stands out because of the different shape language. You can also paint in the ab area as it seems kinda strange exposed like that in my opinion. To me if breaks the idea that she is confident. Seeing as she is a hero, The "V" can stand for victory. So that can be her theme and/or Logo maybe. With her power being able to break the sound barrier with her punches, maybe you has some sound barrier gloves to control her strength. Or you can keep what you have but maybe whenever she's about to punch, a blue aura glows up her fist.
Besides design, I love the face and the hair works for me. She has this peep to her step feel if that makes sense. Giving her that hero smile will definitely work well. Even though the pose is simple it just works to show her confidence.
Hope this helps and I hope you have time to finish.