Considering she had bemoaned about how seriously ill she was and how neglected she'd been etc, I sometimes wonder if Mary was prone to embellishing things or maybe she just looked at things through fish-bowl lenses. Often we saw her exaggerated emotions.

So I wonder if I could believe her when she said she overheard CW's remark. Perhaps after that remark, CW had said something else to Louisa out of earshot e.g. tried to retract or correct or justify it.

In any case, Anne seemed to believe her sister, and as a result was mortified. She repeated the remark to herself a couple of times.

Ch 7: "Altered beyond his knowledge!" Anne fully submitted, in silent, deep mortification.

Ch 7": "So altered that he should not have known her again!" These were words which could not but dwell with her.

While Anne had no reason to believe that Mary had heard incorrectly or out of context or maybe just half the story, I still wonder whether Mary had relayed an accurate information. After all, she was eavesdropping.

Now, considering Mary had heard it as precisely as CW had said it, it was a terrible thing for CW to say. But human nature as it is, we do sometimes say things we wish we could take back. Alas, once words are spoken, they're floating out there somewhere.

I also think that CW probably had no idea that Mary heard what he had said to Louisa regarding Anne. And he had no reason to think that Louisa would tell on him.

I would also venture to add that he probably had no idea how much that would hurt Anne. Considering all that he had done (or not done) from Ch 4-7, at this point (prior to Ch 10) I don't see anywhere that he'd gone out to deliberately hurt her other than simply give her a very cold shoulder.

I would think this is almost similar to Darcy's snide remarks about country dances in PP. He had no idea it would insult Elizabeth Bennet.