Bell, Book and Candle (1958)

A modern-day witch likes her neighbor but despises his fiancee, so she enchants him to love her instead... only to fall in love with him for real. Gillian Holroyd is just your average, modern-day, witch, living in a New York apartment with her Siamese familiar, Pyewacket. But one day a handsome publisher, Shep Henderson walks into her building and Gillian decides she wants him--especially as it turns out he's marrying Merle Kittridge, an old poison penpal from Gillian's college days. So, Gillian casts a spell over Shep. But her powers are in danger of being exorcised by something stronger than the bell-book-and-candle routine: Love.