I'm no pro but the picture is very symmetrical,.. maybe too much so. It would be fun to play off that hard shadow, perhaps positioning the subject in partial light.. focus is tight.. hard light near the arse start to distract if I look too long,.. not a sexual thing, just draws the eye there. A simple light bouncing might provide some interesting fill - I sometimes just grab my trucks window shade. Try some crops to feel out asymmetrical compositions (if you dont have any) and if you can re-shoot.
You might also get closer to the subject's face, seek to capture the moment of expression when she 'goes there'... at the same time defocusing the background with a wider aperture.
-Shea