Who is Mrs. Whitlow from The Last Continent: A Discworld Novel and what is their importance?

Mrs. Whitlow is the head housekeeper at Unseen University (UU), Mrs. Whitlow is known for nourishing soups that either cure or kill and for fine needle work that takes little account of the wearers' dimensions. She is quite prim and proper and speaks in a broad accent suggested by writing the pronoun "I" as "Ai." The wizards are normally afraid of her but find themselves thrown together with her in unusual conditions when she delivers snacks to them on a tropical island reached by stepping through a window in time.