Man(talking to two women of, 1 of them is more attractive thus she is the 'target)',we name her girl A, girl B is her less attractive friend):
Hey, you know what ?! I bet you're a terrible hugger!To girl B Proceeds to hug girl B.
Girl A observes and gets jealous thus her emotional state changes from neutral to hightened attraction due to the jealousy created by the lack of attention given to her. Her friend girl B is getting the attention she craves, so she becomes jealous.