In a parallel universe, Mother Superior was the head of the Sisterhood of Beedlix. She was looking for hymns of her religion in The Library. (AUDIO: The Library in the Body)
She sent a distress signal to the Doctor in order to save them from the end of the universe. She used their song to gain them priority access to the Emporium. She kept plying Bernice Summerfield and the Master with wine. (AUDIO: The Emporium at the End)