At the beginning of Chapter 14, Mrs. Jennings conjectures that:

Col Brandon has money troubles;
Miss Williams is ill (Mrs. J. fancies her rather sickly)
No, it can't be money troubles; he's a prudent man;
his sister in Avignon is worse (even though it said that wasn't it.)

As little as Marianne thinks she has in common with Mrs. J. they both share in these fancies spurred by curiosity. In Chapter 11, Elinor accepts Col. Brandon's short story about a young lady whose acquaintance with the world was disastrous, but Marianne would not have! "But Marianne, in her place, would not have done so little. The whole story would have been speedily formed under her active imagination; and [everything] established in the most melancholy order of disastrous love."

Again, I wonder here if this statement about Marianne comes from Elinor's mind or the narrator's.

Also, I'm always fascinated by 'unreliable narrators' in S&S and Mrs. Jennings conjecturings make me think of how characters can 'spin a tale' whether on purpose or not.