A couple of points with the picture as a whole, the arm holding the gun seams a little thick to me and seems to be detached from her body (try holding your arm in that position with a gap between your body and the arm) the solution to this is to add in the top of the arm going down towards the elbow just below the breast or change the arm to more of an angle and bring the base of the forearm back towards the body. And there is the small point of her index finger being at an impossible angle! All that needs though is an adjustment of the nail!

Her hair needs more definition in the centre just a few lines showing how it moves back from the band then curves over and down her face would improve the look loads.

My final point will be with the gun. It seems to look a little odd... my inclination would be that the end of the barrel is showing too much and you should slightly lengthen the underside of the barrel.

The gun I pretty much accepted would suck, since I've never drawn a gun before. I intended to have less of an angle on the gun, but by the time I was done with it I realized that it was sorta angled towards the viewer more than I wanted, which distorts the view and made it confusing, but was too late to change once I inked it in >_<