yea, agree w/ the above posts, except don't eject yourself. from the very beginning, DON'T REACT to the guy, and keep going with whatever you were doing. if he comes in, and you look at him, the girl will follow your eyes to him and then you've lost the frame. so ignore the guy at the beginning, as if he isn't even there. then keep gaming. have more presence than him - be louder, more grounded, use your body language. then once he's in your frame and reacting to you, you can befriend him for a few seconds, tell him he's cool, and then go back to your girl. or you can AMOG him in front of the girl by poking him in the stomach and telling him he reminds you of your annoying little cousin, or some sht like that
basically once you subcommunicate to the guy he's lower value than you (by not reacting to him), he's not gonna be able to do sht anymore and he's either gonna stand there like a passive idiot or gonna walk away in failure. you're then free to do whatever you want