I agree with Kent's hint. The first thing I thought when reading this was that Wickham has been passing himself off as Fitzwilliam Darcy.
Perhaps now Elizabeth's opinion of Darcy has fallen far enough so that she won't care what he thinks and she will simply come at him in disappointment and anger and tell him what she thinks of his behavior. His answer might surprise her and get the truth-telling on its way. But we are only half-way in the story, so I suppose it can't be so swiftly resolved.
By the way, thank you for this line: "Elizabeth rather thought that Mary helped write the sermons, which was why she was so fond of quoting them", which, if not actually making me laugh out loud,
did make me smile in silence!
