My Sister Eileen (1955)

Two small-town sisters -- an aspiring writer, Ruth (Betty Garrett), and a would-be actress, Eileen (Janet Leigh) -- move to New York City. They find lodging in a shabby apartment and struggle to locate promising gigs. Ruth eventually meets magazine editor Bob Baker (Jack Lemmon), who tells her to write about her life experiences rather than fiction. As it turns out, Eileen's life, with her various romantic encounters, is far more interesting, so Ruth steals the stories for herself.