Other mistake: When EJ gets spooked near the end and turns to face a wall with a doorway to "North Stairway C", she faces the camera with her torch facing the camera directly. However behind her is a perfect shadow on The Wall of herself. This shouldn't be possible as the only source of light, as shown, is from her torch. Cade and Levin are in a different room so couldn't be their torches. (00:39:20)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.