Hmmm, how can I put this nicely? Let's just say I'm not in love with these photos.
In image #1, the focus is off. It looks to be on the tip of her nose, instead of here eyes, where it should be. The image is pretty soft all over. Also, I find the lip piercing to be very distracting (I realize it's the in thing these days, but she's a very pretty girl and it distracts from her eyes). Also, it's a bit grainy for my taste. Were you using a high ISO? Unless you were going for the film grain look it detracts from the headshot. Headshots (if they're to be used to get modeling or acting jobs) should be a straightforward representation of the person and how they look. Nothing fancy.
In image #2 the color balance is all over the place. Her skin is a bit green. Were you using a flourescent bulb? You need to white balance the photos.
Image #3 the same thing, green skin.
Image #4 has the most possibilities. But the shadow on her hair bothers me. You need to use a reflector (or reposition it if you used one). Also the light is very hot on her face. You had the light too close to her. Were you using a bare bulb? A little diffusion goes a long way.
But, hey, you're off to a good start. It takes a bit of tweaking, but it can be done.
Good luck and keep t it.
--
DeanT
http://www.tomasulastudio.com