Josh writes:
The second possibility is that Miller was given some special status or special clearance that was, shall we say, off-the-books, a special status few at the Pentagon or the CIA seem to know about or are willing now to admit knowing about.
Certainly she was going around telling people she had super double secret status:
Miller guarded her exclusive access with ferocity. When the Washington
Post's Barton Gellman overlapped in the unit for a day, Miller instructed
its members that they couldn¹t talk with him. According to Pomeroy, 'She told people that she had clearance to be there and Bart didn't.' (One other witness confirms this account.)