“Poor Old Lady Dithers; she's a sweet old thing to be sure, but prone to bouts of senility. She's recently taken to warbling on about "computer simulations" and "fail-safe" operations. The neighbors sure hope they won't have to commit the old dear.”— Fallout 3 Official Game Guide
T. Dithers is a inhabitant of Vault 112 and like the other Vault Dwellers, Old Lady Dithers is trapped in the Tranquility Lane simulation and subject to Stanislaus Braun's whims. Unlike the others she is at least partially aware of what Stanislaus is doing and tries to alert the others in the simulation but they just treat her like she is crazy. The terminal attached to her pod chair in Vault 112 notes that several readouts show anomalous readings, likely either a cause or symptom of her awareness.
Being one of the very few people who is fully aware of the simulation, the rest of the ignorant populace have declared Dithers as insane and do not believe her. As such, she is considered to be an outcast by the inhabitants.
"We're not really here. We're not really talking. It's all made-up, make-believe. We're sleeping, dreaming. The dream became a nightmare. It has to end, it just has to. But we're not in charge. He is, and he doesn't want us to wake up."
"Did you look? Did you really look? You can't just look with your eyes, you know. Look at Braun. You think he really looks like that little girl? He hides things. Confuses them. You have to find a way to find it."