Exactly. She was not a terrorist. There was not the slightest hint that she might conceivably (short of paranoid delusions) be a terrorist.
Why, then, was she required to produce ID? and told to leave when she didn't show ID? and arrested when she didn't leave?
Well the easy question first. she was arrested for not following orders from a federal officer.
The other answer - read my posts. Apparently there was not the slightest hint that Atta was a terrorist. Apparently the woman who tried to blow herself up in Jordan recently, there was not the slightest hint she was a terrorist. Not enough space here to continue that list..