THE FOUR-SIDED TRIANGLE is a science fiction novel by William F. Sample which was turned into a movie in 1953. And judging by this MovieTome synopsis, it sounds kind of great:

Graduate students Robin Grant (John Van Eyssen) and Bill Leggat (Stephen Murray) have both loved the beautiful Lena (Barbara Payton) since childhood. After years of perseverance by both men, Lena finally chooses Robin, and the two become engaged. Devastated by the news of Lena's plans, Bill uses his latest science experiment, a cloning device that duplicates matter, to create a "new Lena" for himself. Unfortunately, this device performs too well, producing a clone that also loves Robin. Furious and desperate, Bill decieds to use electro-schock to burn the memory of love out of the clone's brain.

(via Roger Ebert's blog)