We never saw the machine tested on anyone but Nora. We don't know that it works at all. We don't even know if Nora went through with it or called it off. The only people watching were Matt and the two scientists. So if she called it off, or if the machine doesn't work, what's the cover up? Matt already agreed to say whatever Nora wanted, and the scientists aren't going to tell everyone their machine doesn't work.
I don't think she went through with it, and I see her story as allegorical, basically a reverse "grass is greener on the other side." Her story was about a parallel world where 98 percent of the people disappeared, where everything was the same except that society's normal functions were severely limited due to there not being enough people to fill the necessary jobs to keep things going (i.e., pilots to fly passenger planes). The loss was tremendous. But in this story, the people closest to her, her family, found a way to move on. Her kids were happy. Her husband found someone else. After the Departure, Nora's livelihood was to investigate claims of whether someone actually departed, a job that a lot of times had her tearing down people dealing with loss. But she never truly dealt with her own loss. The machine gave her a chance to deal with that loss, to tell herself that there was a place where her family was able to move on without her, even though the world as they knew it, had, in a certain way, ended. Perhaps as penance or maybe in some kind of weird solidarity, she decided to live the same way -- in a remote part of the world, alone, in a rural area, where she doesn't even seem to own a car or have any real means of communicating with anyone, except by talking face to face or going to the roadside pay phone. The whole series was about how the world would deal with loss on a massive scale, but what it comes down to is how each individual deals with his/her own loss on a personal level. Kevin's last words to her in the hotel room were "maybe you should go be with them," her kids, but what she really wanted was just to know they're OK, and the hope, for her, was that the machine would give her the answer, that her kids really were OK. But if the machine didn't work, that hope would be destroyed, so she didn't go through with it. Her faith becomes what she hoped would have happened, which became what she believed would have happened, and it's the story she tells Kevin.
