Tell her to CHIRP safery aspects of it and get her to confront the Supervisor telling this person that she wishes to speak to higher management regarding what she has been instructed to do. Also if it is a servisair supervisor advicing her to ignore these rules then she should also contact the airlines duty manager directly and advise him/her what is going on! It is all totally unacceptable!
But also keeping in mind that there are two sides to every story, I hope its a case of your gf is being polite throughout and not being blatently rude throughout leaving the supervisor no choice but to let the passenger away with it as a service recovery procedure as has been my experience with CircusAir before!