Miss Melville Regrets — Evelyn E. Smith

What can a woman do? Susan Melville's trust fund is dwindling, her teaching job is terminated, her lover is abroad for the season, and her apartment is going co-op.
So naturally Miss Melville decides to shoot herself at a posh society party. Unfortunately, she misses -- and kills the guest of honor instead. When she slips out the door, a stranger follows. He thanks her for doing the job for him, and Miss Melville's new career is born.
Of course she has scruples. Miss Melville won't kill just anybody, but she's about to face a job that even she will find a challenge of the most dangerous order, an assignment she just might regret -- for good . . . .