Out on the porch, B asks if Serena's trying to kill her two, but Serena is way over it. Like, she's more done than we've ever seen her. "A guy died, and you use it as part of a game? Who does that?" Blair tries to explain that this isn't a game, this is her drowning and feeling like she has nowhere to stand, and that specifically Yale is specifically her one dream. She feels like S crossed the line by showing up, which may be true but she sure did force it to happen, and frankly Serena wins there too: "And so did you when you brought up Pete!" That is by far the angriest we've ever seen her, it's pretty amazing to see how much Blake's been holding back all along because of how Serena works. "As far as my being here, you take that up with the school."
She turns her back on Blair and heads back inside, but: there it is. Blair's only recourse when she's caged up is to do the most horrific, destructive thing she can think of. All of her insecurities and fears about getting into Yale have a face, now, and what Serena's saying is that it isn't up to either of them what happens. She can't say that Serena's taking it away from her if Serena is essentially powerless in this situation, then she's standing or falling on her own merits, not having anything taken away from her. And, confronted with the facts, she can't think of anything else to do. There's no angle she can play there, if it's true. But instead of accepting that, she pulls a total Blair, which is to say: when Blair doesn't know what to do, she really doesn't know what to do. Which is how Serena ends up getting a purse lobbed at the back of her head. Even the music is scared to start playing.
Serena turns back around, like, Really? "You did not just do that." And Blair does that face she does that's like, Yeah, I kind of can't believe I just did that either, and I scare myself, but suck it anyway. She explains the very simple, kinda awful truth that Serena's not Yale material, and that she was only invited because of her face splattered across Page Six. It makes Serena sad, because of course she's thought about that already. "Face it, Serena. Yale needs to up their Q rating, just like all the other schools, and they're gonna use girls like you to do it." Serena shoves her a little, Blair shoves back, and then boom: total hilarious intense hair-tossing catfight. Serena yells, "And I really hate those stupid headbands!" and a second later Blair screeches, "AHH! My HEADBAND!" and Serena bashes her over the head with the purse over and over, and at some point I swear B goes, "I'm gonna eff you up!" That. Was amazing.