I think "Reader models" are like you guys mentioned, the Teen Vogue girls in features like "Room of One's Own." Other examples perhaps are the women they use to show how different non-model women would incorporate items into their work wardrobe (Vogue did a feature like this), the women who are photographed showing off moves from their exercise routines for fitness/health publications, and so on. They aren't professionals, and they are usually described as something else (by their profession, their age and location and name, etc.) Sometimes they are people with connections to the editors or fashion/social scene in one way or another (many of the Teen Vogue girls or women in Vogue features) or they are people who submit their photos or information through different promotions/contests targeted at readers.