Unless she took the subway to Grand Central for some reason--but then she wouldn't have seen all those hordes of screaming people rushing OUT, she would have been part of the crowd.
I got a freebie 24-hours off on a Monday once. Had nothing to do and no one to do it with so I walked from Gov's Island Ferry to Times Square, it took me from about 9am until dinner time (I wasn't in any big hurry along the way, shopping and stuff)--but was quite a haul.
There is another story where she said she was in Battery Park at the time of the collapse (I know exactly where that is!).
She is not as slick as mom and dad. She better learn to become a better liar or just start telling the truth. Considering the environment in which she was raised, the latter coming to pass is probably remote.