If Hailee Steinfeld wasn't already the queen of Bills Mafia ... someone better get her a crown now -- 'cause she just roasted Buffalo's biggest rivals!!
Josh Allen's fiancée fired off the savage burn during a game of "Truth or Wear" with Who What Wear on Wednesday ... after she was asked to take a "football IQ quiz."
Part of the test required her to list off everyone in the Bills' AFC East division .