Continuity mistake: When Maddie turns the photo album round, its position changes between shots. In the first shot she is holding it by the top of the album, as shown with a brown photo being away from her hands. Camera changes and now she is holding it by the bottom of the album and her hand is on the brown photo. (00:09:40)
Continuity mistake: We see Jenny talking to the former embassy worker. When doing so she has her hands out stretched in one shot and clasped in others. (00:25:30)
Continuity mistake: When DiNozzo mimics sneezing on Nikki she reacts and freezes. Camera changes and her entire position has changed. (00:26:15)
Continuity mistake: When Jenny thanks Nikki for coming in so quickly, Nikki has her coat over her hands, camera changes and now her hands are uncovered. (00:22:00)
Continuity mistake: When the shrink asks if DiNozzo and McGee are a couple, their positions change instantly. (00:18:40)
Continuity mistake: When the CO opens the drawer of Michael's personal effects, the items change place or change entirely between shots. For example a book appears. (00:13:05)
Continuity mistake: When Abby tells McGee that the suspect has a gun, there is an overhead shot of the top of the building and the brown car is at least 4 spaces away from it. When Abby is watching the report on TV and says "damn you Gibbs", the car is next to the building. (00:04:00 - 00:05:00)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.