Is it possible to relight filmed footage with NUKE or After Effects?
I suggest build a real lighting rig and maybe stabilizing her neck.

If you decide to do it afterwards you have to:


Modeling the head and her hair (scan it if this is possible)
Tracking the shots with blender or pftrack
Replacing the head in your favourite package


There are some obstacles: 


To get realistic shadows and highlights you probably need a better rendering engine for nuke 
Detailed modeling is necessary to get the shadow right (espacially for the nose and the hair)
Modeling her hair can be a very difficult task