Selectively blowing out a dark background using aperture/nik software bundle?

[hiphopopotamus]

I have a head shot that I've processed a bit in silver efex pro that I am happy with, but the shot was taken so that the shoulders of the person are coming out of the sides of her head. Because I've processed it to be very white with only small structural detail around the eyes/jawbone/cheeks etc, I'd really like to be able to blow out the shoulders so that they are completely white and only her head is existent in the photo. Unfortunately she was wearing a black strap top at the time. Given my post processing tools (aperture 3 + the whole nik software bundle) is there a way to do this? My first thought was to cut her head out and impose it on a white background, but I don't think I am able to do that with the tools I have. Is there another way?

Cheers

 

[hiphopopotamus]

For anybody wondering - I wasn't able to work out a way to do it with the nik software so I just did it crudely by using the clone tool in aperture

 

[Pookeyhead]

Can we see the photo? It may help.