not that I ever -- Mrs. Cole once whispered to me -- but I immediately said, 'No, Mr. Elton is a most worthy young man -- but' -- In short, I do not think I am particularly quick at those sort of discoveries. (Miss Bates, ch 21)

Mrs Cole is a determined gossip - jotting a letter to Miss Bates as soon as she hears of Mr Elton's betrothal, spreading the news of Jane Fairfax's piano. I suspect she might have put her husband up to asking Mr Knightley about Jane Fairfax, and, in her dinners for the single men, it would not surprise me if she was planning matches -possibly even matching up William Cox with Miss Gilbert that very night.
Ann Cox seems to have been sounding out Harriet's feelings on Robert Martin - maybe not wanting to gazump her friend in attempted seduction, or maybe to spur on a match between Harriet and Mr Martin.