It doesn't mean it's PMS.

It really aggravates me when a girl says something bitchy to a guy and all they say is "Are you PMSing?" or "Are you on your period?" For some girls this can be very embarrassing because either they are and now everybody knew or they say no and all the guys tease her. The thing is that just because a girl is rude or snaps at somebody, doesn't mean that they are on their period. Girls can be bitchy without being on their period.