I have been trying to do a Poser Pro like portrait render, using a free Carrara light set, built-in V4 shaders and my very limited skills.
Here are the results, feel like I am halfway there, but no idea how to improve.
Free lightset from: http://www.sharecg.com/v/28074/gallery/7/Material-and-Shader/V4-Skin-Shader-kit-and-Lights-for-Carrara-6
Just a thought, but you might try lowering your fill light to give more contrast between your key/main light and your rim/backlight. In the image you show, you can see how the shadows are a bit darker on the side of her face. Lowering your fill light might help you achieve this.
You might also try turning off all your lights and starting with your main light, get it the intensity you want and then move on to the next light, get it just right and so on. Sometimes this can help when dealing with a premade light setup.