Dead Rising 2
She appears as the main antagonist in Case West, and is referenced as "The Director" in the game credits. It isn't clear if she's the director of Phenotrans itself, or just the facility.
She has a zombie bite-mark on her left cheek, which has seemingly never healed. She claims that her infection is irrelevant, in that she doesn't need Zombrex anymore as she was cured by an actual antidote for the parasite. Whether this is true or just bluffing remains to be seen.
She also exhibits an extreme misanthropic personality, stating that since the greed of humanity is what created the zombie plague in the first place (referring to the research behind Santa Cabeza, which was intended to double the livestock of cattle) it deserves the zombie apocalypse.
After Harjit Singh's death, she initiates the self-destruct sequence of the facility and escapes with Isabela (still captive). Before departing, she ominously remarks: "Now there will have to be another harvest."
Dead Rising 3
In Dead Rising 3, she is promoted to a higher rank and she and General Hemlock started the outbreak of Los Pedidos. She is searching Los Perdidos for the "orphans" in an attempt to manufacture a cure for zombification. She has put out a wanted poster with a reward of five million dollars for the capture of Nick or Diego.Mallon manages to capture both Nick and Diego as they're exiting the warehouse. She uses a giant laser that grows the larvae to full size, effectively testing if the host is immune to the virus or not. She uses the laser on Diego first, killing him. Queens swarm the lab and start to sting the scientists and soldiers in the room which gives Nick time to escape from his restraints. Mallon manages to find Nick before he is able to escape, and attempts to apprehend him using Loaders found inside the train yard. Nick manages to escape, and Mallon is caught under falling debris before she is found by General Hemlock. During Overtime Mode, she is seen with General Hemlock on a landing pad, while he boasts that they could create outbreaks anywhere they want to, in order to have absolute power over the world. Marian rejects his offer on the grounds that she must find the orphan with the cure, but he claims that the cure is just a myth. In response to her rejection, Hemlock throws her from the landing pad to her death. Hemlock then orders the collection process to begin before the firebombing will follow.