Oddly enough I don't recognize her pistol..I pride myself on my knowledge of handguns and hand-cannons (like .50AE or .67 and especially you .757, you tank of a revolver). It looks like a very broad Desert Eagle .50AE MKXIX or .44 MKVII with the night sights of a M1911A3, but sadly neither is too close to this design. SIGH...research can always be seen by the right eye and you should have done a better job researching or a better job depicting. Great work though...tremendous attention to detail in one area, makes the whole piece need such attention. In other words, if your going for detailed make sure the whole thing is detailed and well researched. Gorgeous stuff.
The simplicity of the background is amazing. There is beauty in a faded wall and coils of barbed wire.
She seems to be a mercenary or a soldier working for an organization (the barcode and the armband gives the impression). She is also covert in her mission, either hiding from her prey or predator, and that she works in the shadows, as seen that she hides behind a wall (and the lighting makes the part she hides in the dark).
Her eyes and hair makes her look masculine, which also makes her androgynous.