I like this a lot, the right hand space helps create a feeling of lonelyness in the dark. I would crop an inch of the empty space above her head though, she looks a bit low in the frame.
Stan, Strobism is the art of using only small flash guns for all your lighting needs, read this article, work your way through the 101, its really interesting.
http://www.strobist.blogspot.com/
I now have 3 flash guns and a remote trigger kit. The flash I used for this cost me £5 in a car boot sale.
If you look in the animal section I have a picture in there titled "Sinister Giraffe", I took it using the same method.