"Can I run a few things past you" means that the man wants to tell the woman a few ideas he has come up with, and wants the woman to give her opinion of the ideas he tells her. The woman, however, has heard the man's ideas before, and believes she already knows what he is going to say. Because she thinks she knows what he will say, she doesn't want to waste time listening to his ideas again. As an alternative interpretation, the woman believe that the man's ideas will be lewd (because the man has been lewd in the past) and does not want to hear more lewd ideas.