The lighting seems a bit too much - highlights are blown out on the right hand side of the face.
I also did a course on portrait photography and 'learned' that all I had to do to change this is to put the lights further away from the model....(and I was thinking that a lot of technical stuff was involved to get the lighting right: it al comes to just moving these lights!)
One teacher set up a mannequin bust (from a shop window) and let us take pictures while he moved the lights around. Back home I could compare the shots and see how much changes while only the lights were moved closer, away and the angle changed.
And start shooting in RAW! That will give you more room to play with the exposures after the model left.
Getting the skintone right is an art on its own, I guess. So that means going back to the trial and error method
In your image, placing the butterfly a bit higher will solve the problem with the eyes. Move the lights a bit away to solve the blown out skin (check the Levels histogram after the first shots).
I think the eyes of the model are very well captured, with just enough light, very beautiful.
Hope this helps a bit...