[U of M Sam]

Opinion:
Stay away from the "knuckle-head" you described. Try to ignore her. Possibly tell her that she is a poor example for all the players, especially her niece.
I see no reason for the coach to bench the player because of her aunt's actions.
How come the players parents did not try to control this individual's comments (someone's sister)? Seems like a deeper situation than we need to know.
I am quite sure I would not do anything as an umpire based on the situation described.
Hope this helps!