"Anne has made up her mind to be happy, even though there is, as yet, no conclusive evidence of FW's regard for her."

Well he has not dropped on bended knee and begged her forgiveness, but his hint at the start of that chapter when he is talking about Benwick, is pretty solid: "A man does not recover from such a devotion of the heart to such a woman! He ought not; he does not."

There have been other little clues as well. His behavior at Mollands was different than ever before. He was off-gaurd. He goes out of his way to be soliticous there as well, which he has done in the past, but this time, combined with his agitation, one gets the impression that he can't do enough to try to show Anne his feelings. Also at the concert, he stays and talks with Anne despite the lag in subject matter from time to time and despite the open snub from her family. He shows that he is willing to weather that Elliot storm of disapproval again.

"Also, I was jarred by Anne's interpretation of the exit line. How optimistic of the girl. In earlier chapters, Anne would have seen it as a dismissal of her person."

Here I agree with you. In earlier chapters Anne would have taken this the wrong way. But it is not entirely down to the reportage of Wentworth not be engaged to Louisa. It has much to do with the gradual change Anne has experienced since Lyme. She is in better looks, better spirits, has gaining confidence and is slowly getting back much of what she lost. To this add the wisdom of those 8 years and she is at last beginning to come into her own. Finally her judgement is not so severe on herself. This is another big step forward for her.