Blair's bulimia.

I didn't realize it either until i read the New York Magazine's Plus and Minus index for this week's episode, it's at the beginning of the episode:
"• Breakfast at the Waldorfs: Cyrus: lox and bagel. Eleanor: fruit. Blair: a croissant. Untouched."
I'm assuming this is their way of mentioning her bulimia, even though it isn't very noticeable, Blair is just sitting there not eating breakfast