A little work on shading and lighting
The main problem I have with the picture is that the glasses don't appear to line up with the eyes. The other issue I have is the lighting on her right shoulder (left when viewing the portrait). The light in the rest of the picture seems to be coming from the right hand side, but on this shoulder it's hard to distinguish where the light is coming from.
To me, it just doesn't seem entirely like a finished piece of work. I really do appreciate the art, but the shading and light source are kind of throwing me off. Keep up the good work though, you really are a talented artist.