Notice, she did not say she was in her office when it hit, only that is was one breezeway away. The Five Sided Foxhole has thousands of people working there.
Now, given all the primitive bonfires about the Pentagon on 9-11, I'm sure that some time during the past seven years, the Heather primitive would've mentioned something. I mean, this is the sort of experience one has, that one can't keep quiet about.
It's more likely the Heather primitive was sitting on a park bench some distance--maybe two or three miles--away from the Pentagon, and saw the airplane crash into it.
However, even more likely, the Heather primitive, being a primitive, probably saw it on television.