Sheila Levine Is Dead and Living in New York(1975)

Painfully shy Sheila Levine moves from Pennsylvania to New York City where she shares an apartment with an extroverted, socially active roommate. When Sheila goes to a nightclub with her roommate, she meets Sam, a doctor who is looking for a one-night stand. She is very attracted to Sam, but he is interested in her vivacious roommate. Sheila goes back to Pennsylvania for a while and then returns to New York with the intent of winning Sam over, but finds that her and her roommate are engaged.