After Serena and Dan recover from the imagery, Dan's like, "You need help getting Chuck to sleep with you? Really?" Blair points out the judgment in his voice, and Serena swears he's working on it, and suddenly he is. "I'm sorry. Uh, no judgment. Only help." In a funny, grossed out-but-nonjudging voice he's like, "So... do you love him?" She screeches loudly that she does not, and he's like, "Why not just lie and say it, then fuck him?" Not exactly the most novel idea, he points out: "Frat guys have been doing that since forever."
Dan writes grotesquely unaware stories about his own life, because he doesn't really understand a reality that doesn't include him (and thus his completely natural but solipsistic viewpoint). Blair turns her whole life into a story so she can remain blissfully unaware, because the last thing she wants is to be included in messy old reality. They're two ways of introverting, but neither of them are all that helpful. B tries for the first time to explain this incredibly huge gulf between them, which in this case is that Dan is painfully literal and doesn't understand things that aren't said out loud, while Blair's desperate to get by on inference and pretense and never actually say anything. Not the sex but the thing behind the sex: "I can't. If I say it, then Chuck wins." He shakes his head. "Right, but if you say it then you get him, and you win." Blair throws up her hands and turns back to Serena. "See? This is totally pointless. I was thinking I would just disappear for a while and give him a taste of life without me." Not when you've both worked overtime to twist Hard To Get into a funhouse Möbius pretzel of insanity, you don't.
Dan chimes in again, this time helpfully, explaining that boys are dumb and forget things that aren't in front of them: "No no no, that's a terrible idea! Don't disappear, become unavoidable. Chuck may be a deviant, but he's still a man. So just... You know, drive him crazy, wear him down." So well done no points off for the obligatory, funny followup: "You should be good at that." Serena smiles and B gives him a backhanded compliment about finally getting interesting, and Serena is all over it, giggling about how nice their little trio has turned out to be, and B flees. "Even broken up, you guys make me nauseous." Serena shrugs and smiles, because why would you turn down awesomeness when the alternative is thinking yourself into a tiny little ball of stress, and meanwhile B's bouncing across the courtyard like those multicolored ping-pong balls in that car commercial.