Who would make whom abundantly regret?

[Sandy]

Background: Jane had been deceived in Miss Bingley’s regard, she realized it when she was in London, Mr. Bingley didn’t meet her, so Jane wrote a letter to Elizabeth.

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This letter gave Elizabeth some pain; but her spirits returned as she considered that Jane would no longer be duped, by the sister at least. All expectation from the brother was now absolutely over. She would not even wish for a renewal of his attentions. His character sunk on every review of it; and as a punishment for him, as well as a possible advantage to Jane, she seriously hoped he might really soon marry Mr. Darcy’s sister, as by Wickham’s account, she would make him abundantly regret what he had thrown away.
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Is it “Miss Darcy would make Mr. Wickham abundantly regret” or “Miss Bennet would make Mr. Bingley abundantly regret”?
If the former, why did the author mention Miss Darcy and Mr. Wickham all of a sudden?
If the later, was Jane that confident? HOW would she make him regret? Why “by Wickham’s account”?

[Kirsten]

Wickham did not give a very flattering account of Darcy's sister. So if Bingley were to marry her, he would regret it because Georgiana would suffer in comparison to Jane.

That's what I took it to mean, anyway. Of course, Wickham is not exactly a reliable source of information, but Jane doesn't know that at this point.

[Kressel]

Kirsten got it right. Mr. Bingley would regret giving up Jane.

[Sandy]

Kirsten wrote: "Wickham did not give a very flattering account of Darcy's sister. So if Bingley were to marry her, he would regret it because Georgiana would suffer in comparison to Jane.

That's what I took it t..."

You are right, I shouldn’t have seen the film before I finish the book. LOL. They hadn’t known the relationship between Mr. Wickham and Miss Darcy yet.

Yes, Mr. Wickham said (Chapter 16) "But she is too much like her brother, very very proud."