where would she lie?
I am not sure anyone questions her citizenship.
If she never recites the Pledge of Allegience or takes any kind of an oath of loyalty to the United States, she would not need to lie.
It could be that she really does not have any loyalty to this country or any other, which would mean she is not lying at all. Some people really are that sophisticated and clever.
Of course, why you would have anybody like that as a friend is your business...
And if TSHTF, you just know your friend is going to be waving her passport and banging on the gates of the nearest US Embassy, pledging loyalty and demanding to be let in.