Well, what i would do is cut some more of the white edges off of the woman, even in the hair and just get creative with that part, however you do it(vector mask, layer mask, etc). People are not as likely to notice, or care when you do this with a vector mask, in fact in a lot of publications, vector masks are used extensively. Or if you know how to cutout hair using channels, go at it. Either way you do it, you need to get some more white out of the edges, unless of course youre going for an outer glow. Which i am assuming youre not. There are a million ways to go at this, but I would likely chose a vector mask mixed with either Filter-->Extract, or other advanced channel operations.
I presume you have two layers? If so Command + Click (PC Control + Click) on the head layer to create a selection. Choose Select > Inverse to select the transparent area of the layer. (You could just have the head layer active and use the magic wand on the transparent area, too.) Now expand the selection (Selection > Modify > Expand...) by two or three pixels or so (which ever gets almost all the white on the shoulders. Now feather the selection by one pixel (Select > Feather...).
Now take the eraser tool and make a huge brush to cover the whole head (use the right bracket key to increase the brush size). Click to erase everything inside the selection which will be just a border around the head and shoulders. That should get rid of most of the white. Now inverse the selection and use the burn tool set to Highlights and about a 20% exposure and go around the hair and shoulders to darken the hair and any remaining highlights on the shoulders and you can end up with a result like the one below.