This is because of the stir the return of Mr. Bingley is causing in Meryton and esoecially the Bennet Household.
Explanation:
Mrs. Bennet being the kind of person she is still firmly believes that Bingley will renew his attentions to Jane, so she wants Mr. Bennet to seek him out to which the latter refuses. This argument which serves as a painful reminder to Jane in regards to Caroline Bingley's actions towards her and the way the Netherfield party left is a bother to her. With the impending arrival of Bingley, all eyes is on Jane and she is feeling uncomfortable.
