Un-Official Critique because I'm not a pro member!
I can see you took some artistic liberties when drawing this (either that, or the one source image I looked at to compare was wrong, as I personally don't know much about Power Girl), as her belt is supposed to be kinda loose and hanging on her right and on her left shoulder the white part of the suit should continue over her high chest, not be cut off by the gold part of the cape. ([link] - source) As far as the artistic critique goes, you did a great job on the hair and the overall shading and form, but the only problem I have is her... uh, around her... eh.. I'm not used to talking about this part of art. Her pubic area ? I suppose, isn't shaded the way I'd expect. There should be more... shape there. (best example I could find [link] ) Super heroines like here were created for their sexual aspect, and detail was typically assured around areas men would generally be looking, so the super tight outfits that were pretty much underwear with half a shit attached came around. The 'underwear' part per-say was fitted like everything else, so should have more form. The way you drew it makes it look like two straight lines that don't curve until the hip (and come to a point? How many pairs of underwear are pointy? OUCH!).
I pointed out the differences between the official Kara and the one you made in-case you actually didn't notice you were using an incorrect image or something, not because I think your too stupid to notice but just to be safe. As always, you are the artist and therefore it is your decision on how to make this deviation, and you are entitled to your artistic liberties. If you dissagree with anything I suggested or pointed out, please remember that they are mear suggestions and not fact. If I offended you in anyway feel free to comment so I can prevent further incidents and apologize for my wrong mistake(s).
Thanks Samous, I appreciate your keen observations. I admit I am new to digital painting and that is the reason I am on DA; to share my works and have people help me where I can improve some more. This is a style I'm still trying to figure out myself and I know I have to learn more about lighting and anatomy. There are plenty of power girl images on the web for reference, I used an action figure I saw at a comic shop for this one. Anyways, thanks again and I appreciate your critique