There is one line that has always puzzled me:
"I may thank you, Eliza, for this piece of civility. Mr. Darcy would never have come so soon to wait upon me."
This is when Darcy and Col Fitzwilliam had just arrived at Rosings and are on their way to visit the Collinses. Now why would Charlotte think this? Did she think that Elizabeth already had some sort of influence over Darcy? Did Charlotte "see" something and came to certain conclusions about Elizabeth's and Darcy's relationship?