You should try to add more details to her face... particularly the nose.... otherwise... it still looks like a sketch... I have a similar problem... nose and face boundaries are quite difficult to make.. :-D
Sure... I might be wrong, but if you look carefully, bethween the part where the nose ends and the lips begin is kinda plane... just like where the boundaries of the face contrasts with the dark shadow of her hair... I always struggle with that because otherwise it makes faces look like a layer put over a dark backround... (I wonder if my English is clear enough to explain my point... sorry)
I think it's fine, and that it's all too easy to overwork a piece if you allow yourself to get insecure over it. My drawing's nowhere near your level of draughtsmanship. My style tends to be a lot looser, and less refined, mainly because I tend to focus on painting, and use drawing as a means of understanding form and facial structure prior to painting. The trick with any kind of traditional art is that you are using layers of marks to simulate depth and movement, and in that respect, you've succeeded here, admirably.