Notice that the girls face has hardly any shadows. This means that the light source, from the perspective of the subject, is large and diffuse.
This can be achieved by a ring flash and shoot close to the subject or, alternatively, put a huge white box behind you.
If you have lots of lights, then 4 strip lights above, left, bottom, right of subject can give you very precise control.
The background is photoshopped because the glow around the subject follows her form. I would love to see a version of these works without this glow.
When in doubt, zoom into the pupil of the face to see the reflection of the light source.
Be careful not to confuse the contrast of the image with the way it was lit. While shadows themselves can't easily be added in post processing, the difference between shadow, midtone and highlight can be adjusted through both lighting and post processing. In particular, by pumping up the contrast in parts of the image (e.g. hair), the "flatness" of other areas is accentuated.
Adjusting contrast based on tone can be achieved with plugins -- for example, Nik's Color Efex Pro tone contrast