Have you considered using a SSS map for the skin? That could improve the skin considerably (although I'm not sure what your restrictions are for this character). I think the hair could use a tad bit more polygons; some parts a bit too hard to be interpreted as flowing hair. I'm guessing the 1bit alpha was a technical restriction as well?
As for the face, I think your proportions and structure are good, but it's the makeup style that's a bit odd. The heavy makeup under the eye is giving her a goth look, but the rest of her doesn't match. Since she seems more like a trampy (no offense, I assume that's what you were going for), Domino-type of character, try focusing on the makeup for the upper eyelid and lessen the bottom tad bit. I think the lip area as someone was mentioning seems "stuck on," I think it's the sharp change of geometry on the bottom part of the lip to the chin.
Now that I look at the nose more, the sides of the nostrils could be fattened a bit more and raised upward - the overall shape of the nose seems a bit too triangular.
Was this character inspired by Mercenaries btw? She sorta reminds me of Fiona Taylor / Jennifer Mui.