Elizabeth & Maria were at Rosings the evening before they left for London. And it seems likely they would thank Lady Catherine for all of her hospitality at that time. The farewell was actually extra-special because "When they parted, Lady Catherine, with great condescension, wished them a good journey, and invited them to come to Hunsford again next year; and Miss De Bourgh exerted herself so far as to curtsey and hold out her hand to both."