The "girl-next-door" was most notable for what she wasn't: Marilyn Monroe. Seductress Monroe represented one end of the spectrum of 1950s female roles, and she was decidedly at the opposite end of the girl next door. In a time of national crisis (first World War II, and later the Cold War), the girl next door offered a wholesome and patriotic image. Harvey argues that the Marilyn-type was on the decline, starting in the 1940s, in favor of the girl next door. The 1950s ideal was "nicer, simpler, younger...more girlish than womanly." Harvey argues that already famous stars of the period, like Lucille Ball, adapted themselves to fit into this model.
Hepburn, who was just becoming famous, didn't have to adapt, but she certainly did fit the part. In Sabrina, she was innocent to the point of being child-like, also reflected by her demure wardrobe and polite way. Her thin body is the opposite of Marilyn Monroe's ample curves, embodying the "girlish" part of the girl, not woman, next door. Harvey argues that this image is emblematic of most female stars, aside from Marilyn Monroe, in the 1950s, an opinion also echoed by Potter (see "I Love You, But..."). Harvey doesn't really get into the implications of this stereotype, or why Monroe was allowed to remain outside of it, but he offers many examples that give a picture of a casting and acting trend of the 1950s.