To start with I think this is an excellent photo. The idea and execution are very good. It does look obviously processed, but it's perfect in the context of where it's most likely to be seen, which is advertising and magazines.
I have done a mod, so there were a couple of things I thought could clean up the photo.
The first was to clean some small blemishes on the skin using the clone stamp tool and the healing brush.
The next was to clean up all the stray and angled strands of hair. This was done using the healing brush and clone stamp tool.
One thing that seemed to draw my eye were the small shadows on the model's knuckles. I lightened these so they weren't so eye catching.
The exposure and shadows were upped very slightly.
Above both brows there is a patch of yellowish colour that doesn't fit with the rest of the colour and tones in the skin. I selected both areas and changed the tone and colour using curves, going into each channel to modify the curve. The selection was feathered so the changes blended into the rest of the skin tones.
The eyelashes on the left have a light patch showing which looks as if it needs another lash to fill the space. I selected an eyelash, duplicated it ( Ctrl J ) so it appeared on its own layer and moved it into position over the small space on the eyeline. I used the transform tool and rotated and scaled the lash to fit. I then used a layer mask to modify the edges so it blended with the rest of the eyelashes.
The lips were lightened along the highlight line and darkened in the shadow areas. This, I hope, gives the lips more of a full, rounded look.
I finally sharpened the details and left the skin and soft areas alone using a layer mask. I may have overdone the sharpening now I come to look at the mod.
These are only suggestions and by no means right or wrong.