Serena spots Nate entering, of course, at just this second, and calls his name just forcefully enough -- and vectored right at the Duchess -- that Catherine jumps and looks over. There's a lot of "Nate?" "Catherine?" and like that, and Serena starts awesomely babbling: "No. No no no, but yeah, but just from Book Club this summer, but that's it, they've had no other personal contact," just like that, while dragging Nate over. She explains the total lies of everything to Nate, about how Blair's dating Catherine's stepson Marcus, and to Catherine, that Nate is Blair's ex. This is so awesome that it causes a rent in time, space and the fourth wall, as even Gossip Girl is like, FUCKING FOR REAL? "What's this? Chuck's date and Blair's date are mother and son? And Nate and Blair are exes? And Nate and the mother are in a Book Club? Now there's a novel plot twist..." I love how even Gossip Girl is finally like, "This show is BANANAS!"
Later, Serena is watching Blair melt down elsewhere on the roof. "This party's a complete bust. My whole life's a bust." Serena tells her it's her own fault -- yeah, she does -- because she was scheming to convince Marcus that she's somebody she isn't. "But my intentions were good. I really do like him. I just... As soon as I knew he liked me, I would have relaxed and dropped the manipulative plotting and devoted myself to being the best girlfriend ever." (Which is so, so true, and one of the many wonderful things about my girl B, but only if you take out the part where this is still and will always be an elaborate ruse designed to drive Chuck insane, so she's speaking in character but talking around the secret ugly thing at the middle of it, which is also totally in character.) Serena agrees and says all she has to do is show the real B to Catherine, and everything will work out. "This is you. Just be yourself." B complains that the D made "Waldorf" rhyme with "Spears," and that she might just as well have "gone commando and held my party at Nyla's Burger Basket." Serena flees from both the self-pity and "denigration of the fine people" of Kentwood LA, and runs off to find Dan after ordering B once more to cheer up.