Dr.Elizabeth McNeil is a UAC Mars Facility Delta Labs researcher, and the one who blowed doctor Betruger's research in Doom 3. She is also the one who asks the UAC board to send Swann and Campbell to the base to investigate the experiments Betruger is running. Although she is not seen in Doom 3, due to Betruger sending her off the planet for her actions, her PDA is left in her office and details her response to the experiments going on in the base and the actions she takes as a result. McNeil appears in Doom 3: Resurrection of Evil, and is the player's leader and commander.
Elizabeth was assigned in the abandoned Mars facility to lead a marine squad who was in the undergrounds of the base . She is seen in the Base command center asking to a marine whats the status of the squad . During the Invasion she was able to escape Eriadu facility and get to a sealed office on Phobos Labs . She informs the marine of the situation and orders him to get back to Phobos Labs . when the Marine gets there , Elizabeth informs him that he needs to shutdown four critical systems in order to get to Delta Labs . She figured out that Betruger was behind this . The marine loses contact with her when he gets to Delta Labs .
In a final cutscene she can be heard, but not seen, talking to the marine and implying that he is "home". This possibly means that McNeil survived the invasion and escaped to Earth .