Philosopher's on Trains: "BITCH!"

I cannot believe that I forgot to share this story with you all last week. You see, I was waiting for the train to start moving, when young couple sat nearby and were talking sweet to one another. Which was fine, but things went sour seconds later:

He: "So you're going?"
She: "Yea. Well, with my mom."
He: "You're not going! I'll get off this train right now."
She: "I'm going with my mom, what's the problem?"
(He gets up and storms off the train--She gets up)
She: "I need my keys!"
He: I don't have your keys!"
She: Yes, you do!"

It went on this poorly acted for a while until they seemed to reconcile their "differences":

She: (inaudible)
He: "I AIN'T YOUR FRIEND, BITCH!"
(He storms off into a different seat 3 rows away--She immediately follows)

For the rest of the trip they were inseparable in each others arms.

I found that perplexing that day, but I recently spoke to someone who was describing the opening scene to Four Christmases (starring Vince Vaughn and Reese Witherspoon) and they do something similar as their way of roleplaying (in a public area). So perhaps that's what these two lovebirds were doing. But what's weird is that then one of their fetishes is having someone be as illogical/annoying as a high school boyfriend.