I agree with you, though the guy blocking the door is truly in a tough spot:
(1) He ain’t a lawyer and shouldn’t be expected to know all that... even if it truly applies to a security situation (there’s a host of rules you sign up for when you’re granted a clearance, which absolutely includes the protection of classified materials from unauthorized personnel);
(2) if he allows her in and shouldn’t have done so, then he’s committed a bad security violation and could be subject to prosecution;
(3) if he blocks her and shouldn’t have done so, that’s at least the safer option by security standards because he protected the classified material inside from someone who didn’t (maybe? probably?) present proper credentials... but he might also lose his job.
I am speculating here, of course, because we don’t know if she was blocked merely because the people on site didn’t want her in the SCIF. That would be a whole ‘nother matter entirely. But there’s a chance this was done for all the right reasons (#3 in my list above).
-PJ