Try a Google Images search on the simple word "model." When I do this, Google shows me hundreds of images, mostly women and a few men, all beautiful in the ways "models" are usually beautiful. 

When I read your sentence, this is the idea I get:

Gideon's wife once worked professionally. She earned a living by modeling for photographs. The photographs probably appeared in places like product advertisements, and clothing catalogs, and possibly magazine covers.

The basic idea of "model" here is "a  person who poses for an artist." If the artist is a painter, the model has to "hold a pose," remain still in one position, while the artist works. Photographers' models follow the photographers' directions. Fashion models show off a designer's clothes, while they walk down a runway at a fashion show.

In the United States, when we think of "a model," we usually think of person with "perfect" physical beauty. Usually she is not just "beautiful in her own way," but one who fits our cultural norms and stereotypes of the ideal physical appearance. (Cindy Crawford has a mole on one cheek. Nevertheless, she became a "supermodel." But that is unusual.)

In the United States, traditionally, our ideal of beauty is youthful beauty. There are modeling jobs for older women, but as women age, there are fewer and fewer modeling jobs. Therefore, modeling careers tend to be short. It is not unusual to hear of people like Gideon's wife who had a modeling career when they were young.

 Here "model" ,means someone whose job is to show <a class="defRef" title="clothe" href="https://www.ldoceonline.com/dictionary/clothe" style="border-top: none; border-right: none; border-bottom: thin dotted gray; border-left: none; border-image: initial; margin: 0px; padding: 0px; line-height: 1.5em; color: inherit; text-decoration: inherit; transition: color 0.5s ease 0s, background-color 0.5s ease 0s;">clothes</a>, <a class="defRef" title="hairstyle" href="https://www.ldoceonline.com/dictionary/hairstyle" style="border-top: none; border-right: none; border-bottom: thin dotted gray; border-left: none; border-image: initial; margin: 0px; padding: 0px; line-height: 1.5em; color: inherit; text-decoration: inherit; transition: color 0.5s ease 0s, background-color 0.5s ease 0s;">hairstyles</a> etc by wearing them at <a class="defRef" title="fashion" href="https://www.ldoceonline.com/dictionary/fashion" style="border-top: none; border-right: none; border-bottom: thin dotted gray; border-left: none; border-image: initial; margin: 0px; padding: 0px; line-height: 1.5em; color: inherit; text-decoration: inherit; transition: color 0.5s ease 0s, background-color 0.5s ease 0s;">fashion</a> shows or for <a class="defRef" title="photograph" href="https://www.ldoceonline.com/dictionary/photograph" style="border-top: none; border-right: none; border-bottom: thin dotted gray; border-left: none; border-image: initial; margin: 0px; padding: 0px; line-height: 1.5em; color: inherit; text-decoration: inherit; transition: color 0.5s ease 0s, background-color 0.5s ease 0s;">photographs</a>. In this context, "as a model" means the early days that she'd started her job as a model.