Fiona on Fire (1978)

Fiona, a rich, beautiful and successful model in New York City, is found shot to death, and her fiance, Steven becomes the prime suspect. The tough detective, Wilbur assigned to the case discovers that she has kept a small book with information about all her friends and lovers. When he begins to look into the people whose names are in the book, he begins to uncover some disturbing information about the kind of life that she actually led.