Just for fun, don't take this seriously...
Anyway, I have been thinking the and it is quite clear the it is just another version of the legend of Pocahontas, especially the Disney's vetsion of it.
The demons are analogue to the native Americans, who just wanted to live in peace but where forced to fight against a powerful, greedy conqueror (the UAC) who came to steal their natural resources (the Argent energy) and enslave the demons for cheap workforce.
Olivia Pierce is the John Smith of Doom, as she turns against her own kind to protect the natives from being oppressed. Unfortunately in this version of Pocahontas, governor Ratcliffe (Doomguy) is victorious because of the players intervention.
It is bit irrelevant who plays the part of Pocahontas in this version, but most likely it will be Cyberdemon as that thing has to adapt to the conquerors manner as well due the cybernetic augmentations.