I can only speak for myself, but I definitely try to support companies that are promoting plus-size beauty, whenever possible. If I can purchase a similar item at one store or another, and only one of the two is using plus-size models, that's the one I will turn to, every time.
By the way, the model you posted, Torrid's "Snow White," really is my favorite among that company's many girls. She is the curviest and the prettiest, which makes for a very positive combination. I thought she looked very confident and very beautiful in this picture (longer hair, too)- and the sweater looks quite cozy.