This is beautiful, and it's not just about the model (though of course that helps...) What I think works about it is the way that both her blouse and hair are "puffed up"; it doesn't feel like a static portrait, but rather it feels more like she's expanding into it, making the space her own. The light is extremely good too; there's enough to make the presence of the background felt and therefore provide some depth behind her, but it's so subtle that it doesn't compete against the main subject.
