Bell Book and Candle (1958)

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.