Mother Proudfoot is the chief attendant in the Temple of the Living Asheth, where she serves as the guardian of the young girl who has been chosen as the current incarnation of the Goddess Asheth.
In the Lives of Christopher Chant, she functions as the grownup authority whom Christopher is always trying to avoid when he visits the Goddess' quarters. When the current Goddess escapes and spirit travels into Christopher's world, she brings a kitten whom she has also named "Proudfoot" after her former guardian, who she seems to have been quite fond of.
Later, after the huge battle with the Wraith which is finally won by the inhabitants of the Castle with the major help of Christopher and the Goddess, Mother Proudfoot suddenly appears herself in the Castle's pentagram, bringing with her a chest of uncut diamonds. She announces that she is the magical leader of her world, and wishes to request that Chrestomanci De Witt take over the guardianship of the Goddess, and use the jewels to fund her at a respectable boarding school. The Goddess rushes to embrace and thank her, and announces that she will take the name "Millie" in Christopher's world, after the heroine in the girl's boarding school novel Christopher had brought her.
Mother Proudfoot disappears back to her job as guardian of the next Living Goddess and is not heard from again.