When tea was over, Mr. Hurst reminded his sister-in-law of the card-table -- but in vain. She had obtained private intelligence that Mr. Darcy did not wish for cards; and Mr. Hurst soon found even his open petition rejected.

How did Caroline obtain this private intelligence about Darcy not wishing for cards? Ask him herself? I suppose that is possible as they were walking out together alone in the shrubbery in the previous chapter.

It also brings to mind why Mr. Darcy did not wish for cards... He plays the first night Elizabeth arrives. Perhaps he's just annoyed with Caroline's fawning over him, but I also considered that he might have noticed that Elizabeth politely refused yet ended up observing the game without playing. Mr. Darcy felt the rudeness of excluding EB whilst walking with the Bingley sisters. He semms to notice everything else, including the novel attention that CB pays EB! We also know he's clever.