I like the pose and the angle, but i definitely think you need a fill light. the shadow on the face is too harsh. i like the shallow depth of field, too.
??? Did you use your 50mm f1.8 for this shot, as the focus / out of focus does not work for this shot, maybe a little more light in general, but also some fill in from models left and from behind maybe, also try a slower shutter speed and tripod to give a little noise to the shot, portrait work can transform with the use of direct and indirect soft lighting and maybee taking more shots from different positions, and Head positions as head back for this shot may be a lot better with lighting use and skin colour adjustments, Cheers Steve