Under Covers - S3-E8
Character mistake: In one scene, Jenny refers to "the former Czech Republic." That is the state's current name; it was formerly a part of Czechoslovakia.
Character mistake: Dr. Ducky mentions that the inventor of the guillotine in France was Dr. Joseph-Ignace Guillotin, but it was actually Dr. Antoine Louis.
Character mistake: When Gibbs tells William Danforth that the body in autopsy isn't his son, he says, "Not according to AFIS." AFIS is the fingerprint database; since the body was identified using DNA, Gibbs meant to say "CODIS." (00:13:50)
Chosen answer: It is never stated, however she must have been there several years if she is on presidential detail.