Louisa is the talking portrait of a woman hanging from the Magic Cupboard located in the Spellman kitchen. She lets the Spellmans know when they're missing ingredients from the cupboard and sometimes gives them messages from the Other Realm. Louisa stopped making speaking appearances during the college seasons but spoke one final time in the Season 7 episode "In Sabrina We Trust."
In the early speaking appearances, Louisa was voiced by Caroline Rhea who played Hilda, but her voice was electronically sped up so nobody would recognize it. Annie O'Donnell provided the voice of Louisa in her last speaking appearance.
She may be a reference to famous writer, Louisa May Alcott.