I can see the points that you have brought up to defend the ON. I agree that right when the ON tells us that Miss Bingley is not yet desperate she is not, at that moment. But I still think her need to ask Elizabeth to take a turn about the room and sneaking out on a walk with Mr Darcy without informing even her sister at Neeverythingtherfield was desperate moves on her side. And only a short time after the ONs statement she has to attack Elisabeth with the thoughts of Wickham and after the visit first tell Miss Darcy everything she can find to critize Eliza and even feel the need to repeat it to Mr Darcy. When I read the novel I picture Caroline as very stiff and insulted that she has to endure such a company but switch to her smiling admiringly at Darcy and forcing her smile to stay when she looks at Elizabeth so she won´t come across as petty-minded and then spoiling it with her words.