Factual error: The intro shows a flashback from 1994 where young McGee is using a PC with Windows 95, which was not released until late 1995. (00:00:35)
Revealing mistake: When Gibbs' flip phone started ringing, and he flipped it open to answer it, for the brief second, in the closeup shot of the flip phone, the screen on the phone says "No Service" despite receiving an incoming call.
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.