I really like the pose and expression you have going on here. Her face and her hair came out fantastic. Her torso/abdomen seems a bit on the long side though, and by extension of that, I think her hips and legs wound up coming out a little too wide. It's almost as if it's a Supergirl from two different drawing pasted together. You might be able to see what I mean if you hold your hand in front of her, cover above the belly button, then cover below it. Given the size of her upper body, I think if some of the space between her belly button and the waistline on her skirt was removed and the lower body was scaled down a bit, it'd make her appear more natural.

The lighting also came out fantastic, but the colors feel a little muted to me. Maybe it's the white background, maybe you intended it to be that way, but I feel like since the background is solid white, her skintones and costume should have more saturation/vibrancy to them, at least in the shadowed areas. To me the white background helps make it appear extremely bright, so the shadowed areas, while darker, would not lose as much saturation. Other than that, keep up the great work!