The anatomy and expression are really good - not much to improve there, if you ask me! Her hair is really well-drawn, too - I like the way you coloured it.
A good thing to try is to use more colours when shading - don't just use darker green to shade a green object! For example, she's sitting on a brown flower-middle, so some of that reddish colour should reflect on her pants, the petals, and so on. Using other colours in the shadows can do wonders for the depth of the drawing! (blatant plug: a colour tutorial I wrote: http://www.idenise.net/misc/art/colourtut/))
I really like her costume - like Li-Chan, I think the blue thing rather clashes with her green/red outfit, but that's quite minor. Her wings look like stained glass...that's another thing I like!
Good work, overall - I really like this picture, and I'm sure the requester will, too. :)
Your lineart and design are excellent, you've got anatomy down pretty darned well, and the character herself seems to be well colored. The only flaw is the one you yourself mentioned--that you were rushed and didn't take time to finish the coloring. Well, you know, it still looks good but could definetly be better, if the lovely shading-highlighting you did on her hair and shirt are any indication of your coloring skills.
Her legs don't look quite right, though. I think they need some more lines, for example, outlining the kneecap, to show what's going on in them more. I'm guessing you draw faces and torsos more than legs, since the face and torso here are incredibly well drawn. Keep working on lower anatomy, though, you'll get it in no time at all.
I love the details in this image--from her jewelry to the transparency of her lower wings. I just wish there was more of a background so you could show off the transparency of the wings more in the upper half. My only other critique? It's quite silly, really, but I don't like the blue thing on her forehead. The blue just doesn't seem to match her green color scheme.
I'm definetly impressed by your work and will be adding you to my museum, for sure!