The illustration above for a romance story in a women's magazine from 1959 (I'm not sure which one) was done by Coby Whitmore, who specialized in such stories and in magazine ads for women's products.

Whitmore was part of a new wave in magazine illustration in the late Forties that broke away from the Norman Rockwell school — but not too far.  The artists of this generation still relied on an almost photorealistic draftsmanship but began to get freer, more painterly, with the treatment of the surface of the image and moved towards bolder graphic effects in the overall design.  Backgrounds often became highly abstracted — a contrast to the meticulously rendered environments of Rockwell's most characteristic work.  The image below is an illustration for a romance story in a 1957 issue of Good Housekeeping:

The images of the new-wave artists still had a strong narrative element but it was more intimate, trying to capture fleeting moments and moods, focusing on the characters depicted with a view to glamorizing them.

This approach would come to dominate pulp-fiction paperback covers in the late Fifties and Sixties and informs the style of artists like Robert McGinnis.  It's also related to the photorealistic but graphically striking soap-opera comic strips of the Fifties like Mary Perkins On Stage.