1st one is the strongest for me. 2nd one, well, she just looks a bit miserable
My advice would be to get the model further from the wall, it's slightly distracting (in general) and you can also avoid unwanted shadows.
3rd is nice just not sure on the black background but she looks happier
I've only done a few portraits with good lighting (flashes) but you could do a lot worse than taking a look through the strobist website (check the lighting 101 and 102 links on the right side).
I don't know what kit you have but I have 3 flash guns with radio triggers, a couple of shoot through umbrellas and a largish softbox.
If you are prepared to set flashes manually (a lot easier than it sounds) some cheap radio triggers and flashes with flash stands and diffusers would only set you back around £200.
Here is an example I did last week, bare in mind I've only been using flashes for a short time but once you get the hang of it it's straightforward. Probably some technical errors on mine but these were only to practice set ups etc. This was with 3 flashes, two behind, 1 camera right with softbox (you should be able to tell where they are coming from).
On a side note, I'd try and use a longer focal length lens, I used my 50mm f/1.4 and 105mm f/2.5 and you can tell the difference in how the face is distorted more at 50mm. Longer focal lengths means you don't have to be as close/intrusive on the model and still get a nice tight shot, guess it depends on what you want to achieve.
The first 2 are with 105mm, the last (in red scarf) are with the 50mm, hopefully you can see what I mean.
If you want to go down the single flash setup there are good sections on strobist, it's mainly about positioning of the light/working with the sun etc.
Otherwise good first efforts, they are exposed nicely, I can't tell what lighting you were using but it looks like multiple small lights in front and below?
I'll happily remove my images if you want me to, they were just for an example.
