Yeah, I'm not a fan of the New 52 Supergirl DC. The book was pretty good, from what I read of it, but the design is... unfortunate. I most like the DCAU white t-shirt look myself -- but then it's used by Linda Danvers, my favourite Supergirl, so I'm undoubtedly biased.
Er, anyway... you did an image here. Right. Let's talk about that.
Good work. You keep improving! I really like the little wrinkles on her sleeve and skirt. Nitpicks: first, the gold edging on her top goes into her arm a bit (on the left). Second, the hair is pretty smudgy/blurry at the edges and also seems to fade noticably at the bottom. I'd guess this is due to your trying to blend hair into the background to avoid jagged edges. If so, blurring isn't really the best way to do so. Better to antialias/feather your selection when cutting it out in the first place, which makes for smoother edges. Painting in the hair by hand is also an option, albeit neither quick nor easy.