One step back: When a person flirts with you while being in a relationship, don't be surprised if you hear sudden references to his or her partner. If a flirt is prolonging the period of teasing somebody, chances are that the reference will come up once in a week. But, come it will. If you have any doubts about the intention of the flirt although you ideally should not, that one reference will be enough to tell you that s/he has been fooling around all along.