Blair opens the envelope, backed against a tree, and she shivers. Sad, a little scared, mostly like the world just got heavier. Oh, girl. Either way it was going to suck. You were right.
Blair comes to the Empire, where Chuck is sitting in some very moody light and is not at all interested in talking to her. In fact, he accuses her of being a plant by Humphrey to get him to feel something, which shows that he's learning how a Humphrey operates. Finally, she just sucks it up and speaks: "I'm pregnant. It's Louis'." His face falls without moving and she steps forward; he raises one hand off the bar, like a rattler, so she stops moving.
"I didn't want you to find out from someone else, and wonder if the baby was yours..."
"That's very considerate," Chuck hisses, which: There's your answer. She throws her shoulders back and goes for breezy. "Yes, well. If I know anything about Chuck Bass, it's that fatherhood isn't part of the lifestyle." He won't say it, so she goes on looking. He's not really quite ready to let her go, so he just sends off a weak little twist, like a kitten batting at your hand: "...You must have been very relieved when you realized you weren't carrying my offspring. That certainly would have derailed your fairy tale."
Which is another answer, entirely. The opposite answer. The one she kind of wanted when she walked in. I cannot say enough good things about the acting in this scene, but the writing's also there. Like Blair, just unbelievably so: "This fairy tale is... Complicated."
Ah, now I get the thing with the dog: She saw him handing the dog off and assumed, as we were probably meant to assume, that he was getting rid of it. Meaning that he is still in no position, because he's too busy snorting and fucking to take care of a dog, much less a broken fairytale. And what's awesome about that is, she wasn't actually ever avoiding the question: She was telling two stories at the same time, and freaking out about both of them, and loving both of them, and she didn't want either of them to end. I wasn't entirely sure which angle she was playing until the puppy, who comes running in right on cue. Her eyes light up, a little. The dog's name, of course, is Monkey.