...Well, it's pretty much the same thing. So Blair has been yelling for probably ten minutes at Serena's place of business about this, about Chuck "choosing" Serena over Blair, which is a tossed-off line in the scene but is actually really important, because that's how it looks to her -- and that Serena and Chuck are in Grownup Club and she's useless -- but because that triangle keeps iterating for the whole episode. Serena shushes her in vain, reminding her that this club opening has to be a secret from KC for the nonce: "The only way I can prove myself to KC is if she doesn't find out about this party until after I make it amazing." Not to mention she'll steal it -- or as Serena more wisely says, "take it away" -- because it's a huge fucking deal.
"It's not like Chuck hasn't kissed a guy before! He said so himself!" (Oh, Season Five Previouslies, how I will adore you.) Serena, finally annoyed and flaring a little nostril, sharply advises Blair to get over herself. "Did it ever occur to you that maybe it's not about the kiss? Your game is based on trust, and you broke his." Blair gives a nutty protest that Chuck "pretending he's not mad" at her -- which is actually less nutty, since he just admitted that's exactly what he's doing -- is way more untrustworthy. "I'm going to demand he let me help him..."
Serena raises her voice and tells Blair the surprising truth: Today is not about her. Blair, having never met a day that wasn't about her, even when she wasn't wobbling like a blowout waiting to happen, is flummoxed. "Chuck has 24 hours to create something from scratch. His liquor license hasn't even cleared yet..." And if the phone hadn't rung right then, I'd like to think that Serena would have noticed the crazy gleam come back into Blair's eyes when she said that, and intervened. But no, because it's fussy Chuck calling to doublecheck one more thing, she lovingly deals with him and hangs up after B has had time to put her normal face back on over her totally insane face.
"I know Chuck is anti-everything Bart Bass, but his father must have had a better way to get these things done," Serena says, taking a match to the powder keg of crazy plans already spinning in Blair's head, and finally notices that Blair has gone to Schemeville. "Have you even been listening to anything I've been saying to you?" Blair gets spookier than she's been in a long time, perfectly composed and sort of vibrating as she repeats that this isn't about her, it's about Chuck, and therefore she is going home. Then she stiffly turns, grabs a bag, and makes her scariest face yet where Serena can't see it.