How is it impudent or unworldly to say that you have no feelings for a man and would not accept him if he proposed? And it may not be discreet to say so, but I do not think it is indiscreet enough to be a flaw.

And remember that Anne is not abusing him here. In the same paragraph she has said I consider him with great respect. I have no reason, from anything that has fallen within my observation, to do otherwise. She is not abusing him, she is simply saying that she has no love for him. This may be hard for Mr Elliot, but it would be harder on Anne to expect her to lie about her affections for him, and harder on Mr Elliot if the lie got back to him and then he later was refused.

I do not think there was a rule of etiquette banning a woman from saying to a friend that she felt no affection for a man. And I can think of other cases where JA's heroines did this without any criticism by her of this. In NA, Catherine Morland tells Isabella Thorpe that she feels and felt no affection for John Thorpe, in Emma, Emma tells Miss Taylor that she has no feelings for Frank Churchill, in P&P Elizabeth tells Jane that Darcy proposed to her and was refused. While Elizabeth and Emma were confiding in someone who they trusted deeply, Catherine's situation was more similiar to Anne's in that she was being assumed to return a man's affections when she did not. What is your evidence that JA would regard this as immoral?