Serena explains to Blair that the honeymoon is supposed to end. Her voice is very amazingly firm in this whole scene, like, she understands that Blair is close to losing something and she really doesn't want her to, so she has to cross her eyes and force herself to actually exist in the world long enough to explain these things before Blair gets blown away again. "It isn't real. The real part is when you settle down with each other. The three-month milestone." Sweet. Blair pronounces this not a milestone but a gravestone: "Settling down means death. Less sex, more silence. We found a way to avoid that that works for us." She gives a brilliant smile, but it's a bummer.
The only thing worse than being controlled by your actual boyfriend is being controlled by/trying to please your imaginary mind-boyfriend. Either way, you're abstracting away from who you actually are, who is somebody Blair's always had trouble reaching. She's turning Chuck Bass into a movie. "...Sure about that? I mean, if you don't mind me saying so..." Chuck tells Nate to stop playing the Jules & Jim card and move along, and Nate agrees, because of course Nate is a huge Truffaut fan, and he's like, "What if Blair is doing all this creepy shit to please you? And has no idea that she's even doing it? Because that's her entire life?" And separate from the homoerotic orbit they're in all the time, Nate really does know more about Blair's narrative addiction, because while Chuck's role was to play monster, and then prey, and then redeemed, Nate's only ever had to play Nate.
"If you love him, then lock him down. Open relationships only invite chaos!" Blair points out that it's not really an open relationship (and stop getting A-Rose all over it now that he's my brother and Chuck is yours) because they are actually monogamous. "It's just one of our games, like the rest." Serena attacks Blair's vulnerable spot, which is time management: "B, college is about to start. What happens when one day you don't get there in time?" Before Blair can press her and try to make sense of this particular objection, the paparazzi arrive again and S fakely groans, "I still have no idea why they're following me!"