Thank you. I mostly made the assumption because she seemed to mostly act as a liaison between the FF and everyone else (like Mycroft Holmes).That "secretary" is actually the head of the Future Foundation. Not that you would really know that; I made the same assumption but looked it up before I posted it elsewhere. It is honestly wild how much of this movie is directly focused on the Fantastic Four and no one else.
I wonder if she had a bigger role in some earlier version of the script because she was in the "big role" part of the credits before the mid-credits scene.