|The following is based on Fallout Tactics and some details might contradict canon.|
She is mentioned by Simon Barnaky, his holotape, and some of General Dekker's debriefings connected to the case of Simon Barnaky's abduction. It is known that she shares the General's beliefs that the mutants are abominations that should be exterminated. At the end of game, when Simon Barnaky is revealed to be alive (even though not a human any longer), but became the Calculator's ally, it was the memory of Maria that enables him to stop fighting the Warrior and, if needed, take control of the Calculator himself.
Maria Barnaky is mentioned only in Fallout Tactics.