Uh, Not Sure This is How "Beguile" is Supposed to Work LOL

Using the romantic action that you get with this reward makes completing the Serial Romantic aspiration a breeze. It's just as @MasonGamer described, basically a sort of 'cupid's arrow'. If you don't use this romantic interaction then apart from the fact that most of the other 'normal' romantic interactions will seldom fail, there is nothing automatic that will happen for a sim with this reward trait.