-USED WITH PERMISSION-
The model I used is "Lara Croft HD" by masked_marauder (the best chick-mod creator). I did textures myself.
The files to overwrite are "bfybe.dff" and "bfybe.txd" for the casual outfit.
The files to overwrite are "WFYLG.dff" and "WFLYG.txd" for the beach outfit.
MAKE BACKUP FILES BEFORE OVERWRITING.
 The Doppelganger (Casual) can be found near the beach and the Doppelganger (Beach Outfit) in the beach (photos).

Skins won't work, so if you want Doppelganger as a player model, overwrite files with any of the pick-up clothes.