...slighting Lizzy. I consider their friendship as honest and above-board. In fact Charlotte is quite open with Lizzy about her differing opinions in fixing a potential spouse, but Lizzy does not yet seem able to believe that Charlotte's feelings could differ from her own; Lizzy does not realize that two intelligent people can honestly differ.

Yes, Charlotte is a master player at the courting "game" (as a game with rules and strategies); certainly she has been at it longer than almost anyone else in her set of friends. Like Lizzy and Darcy (and Mr. Bennet), Charlotte is a "studier" of people. At 27 Charlotte is potentially more desperate than her younger friends and is willing to consider playing the courting game for higher stakes: what she is saying here is that, if Jane thinks she likes Bingley, she should not miss the opportunity by being timid. Perhaps Charlotte is speaking from her own past experience; we do not know.