So the whole time Chuck is like, "Fuck this lady for showing up and making me feel crazy," Serena is all the way up his ass about her dad. Nothing that comes out of her mouth from this point forward is more than tangentially about Chuck at all, and it's just brutal. "You don't seem excited. After all this time of thinking your [father] is gone, now you have a second chance! [H]e's here now, who cares why? You have no idea what happened twenty years ago, why [he] stayed away. You have to at least let [him] explain!"
Blair, now torn between the real and present pain that Chuck's going through and the very clear mental place Serena is charging into, just stares. Chuck heads down to the bar for a drink, telling them they're welcome to the hotel safe combo if they want to violate him a little bit more. When he leaves, Nate's like, "...He'll be fine," and Serena's like, "[I'm] acting CRAZY!" Blair mans the eff up, just incandescent throughout the episode, and tells them in no uncertain terms that they will leave him the hell alone. "You didn't see his face when he confronted this woman and she sent him away. He's had enough pain in his life. If he doesn't want to hear her story, then I'm going to respect that. And so will you."
And I mean, there's a whole motif here, the "hear your story" thing, that comes up in every storyline -- even Jenny has Damien's daddy issues to contend with -- and it's a fairly sensible way to collect the threads. Because Chuck is so next-level that he's making this sort of existential choice to just block Elizabeth altogether: His mom or not his mom, it's the story he can't handle. And Serena's generating a story a minute, and has been doing so since Santorini, each one sadder and more pathetic than the last.