I remember when Emma was trying to appear more interested in Frank Churchill's arrival than she was, and took the opposite side to Mr. Knightley in the 'should Frank visit Mrs. Weston' argument in ch. 18. In that argument, I think Mr. Knightley was also being a little dishonest.

"Prejudiced! I am not prejudiced." [...] "[Frank Churchill] is a person I never think of from one month's end to another [...]"

In ch. 43, she is trying to appear happier than she is, and is again acting against her own judgment. She did try to mute Mr. Churchill's liveliness early on, but not with much effort -- and no effect.

Had she succeeded, perhaps Miss Bates's feelings would have been saved. But perhaps that would have put off Miss Woodhouse's needed lessons to an indefinite future time.