In chapter 47 Jane tells us that Mary and Kitty has been freed of the duty of sitting with Mrs Bennet. In chapter 49 we find both of them with Mrs Bennet when Jane and Lizzy comes to tell the good news of Lydia being soon married.

Can it be that Mrs Gardiner has had a talk with the younger miss Bennets telling them to give Jane some rest? Or could Lizzy have authority enough to change Janes decision. But then again Mr Bennet has returned from London so it might be his authority. Or maybe Mary has been thrown out of the library so Mr Bennet can use it. What could make Mary and Kitty leave their "worthwhile" occupations to sit with theirmother?