Blair's "What was wrong with me?" reaction is impeccably in-character, too.

I love then hints of vulnerability in Blair. Vulnerable insecure Blair is just as fantastic as bitch!blair and makes me want to hug her and never let her go.

Oh Blair-bear, you secretly vulnerable poor thing. Just come over, I'll love you unconditionally.

You're going to have to pry her out/off of Serena's legs lips arms.