I am sorry to cause anyone pain (;D) but I think you were right to suggest Anne felt it correct to have done her duty rather than to hold on to her hearts desire. I can see why it does not sit well with you; it grates on modern sensibilities of going for what you want regardless of the risks but I think it did sit well in JA’s era. Even lively Lizzy Bennet (P&P) does not seriously think to connect herself to Wickham, a penniless officer, when she is forced to think about it by Aunt Gardiner. Back to Persuasion; I think there is a difference in Anne’s feelings between Ch. 4 and 23 but not a great one. To me there are two sides to Anne’s feelings about her decision to end the engagement. One is the romantic side that regrets her decision especially since the dangers of the situation are cleared up rather quickly; the other side is in feeling she had done right by (as you say) her duty to Lady Russell but also to Frederick.

In Ch. 4 Anne does not blame Lady Russell for her advice or herself for taking it because she owed Lady Russell the duty of a daughter, “Lady Russell, whom she had always loved and relied on, could not, with such steadiness of opinion, and such tenderness of manner, be continually advising her in vain.” Anne was willing to go against her father and sister because they are foolish and uncaring but Lady Russell’s advice was sound and she cared. Simultaneously Anne believed she would have been happier suffering all the anxieties of a long engagement because the rewards of their felicity, of her belief and hope in Frederick would have been enough to sustain her, “Such confidence, powerful in its own warmth, and bewitching in the wit which often expressed it, must have been enough for Anne.” I think, for Anne it became choosing or not choosing to place herself in a situation where those who love her would worry for her future. Anne’s seemingly contradictory feelings only make sense if you believe children had a duty to their parents in their choice—at nineteen Anne felt she did.

Mutual affection which crowned an advantageous match was a welcome blessing, but immoderate passion leading couples to disregard other criteria was thought near-insane.

The Gentleman’s Daughter, Women’s Lives in Georgian England, Chapter 2, Love & Duty, page 41 by Amanda Vickery.

IMO by Ch. 23 events crystallized Anne’s feelings about her decision to end the engagement. Anne was insensible to danger when she accepted Frederick so Louisa’s insensibility to danger and its terrible end IMO served to reinforce her decision on the side of prudence. Anne feels morally correct, “I was perfectly right in being guided by the friend whom you will love better than you do now. To me, she was in place of a parent.” If she had ignored her duty I can easily believe Anne when she says “I should have suffered more in continuing the engagement than I did even in giving it up, because I should have suffered in my conscience”. This is a hyped up version of what she said in Ch. 4 about not blaming Lady Russell or herself. As you say, it is only events which make Lady Russell’s advice wrong so Anne believes she was correct to put her duty to a parent before that of making an exquisitely delightful but imprudent choice—the near insanity of embarking on a long engagement without any real source of security. Just my opinion of course. (:D)