Ashley's hair cannot simply be "Gibbed" in for FemShep, nor does it work if you just mess about with the vertices in Gibbed. The hair sits on the skull mesh, and Ash and Shep's meshes are very different.
The only way I know of so far to get Ash's hair is to change a shoulder slot (armor gear) to the Ashley hair mesh, then "equip" the hair. Obviously any scenes where Shep isn't in armor won't work.