First, the image is reversed, note the labeling. Her right leg is well forward, and her left leg is well back, but they’re lined up in a way that suggests she is standing straight. The back side of her neck is being eclipsed by her hair in a way that makes her neck look freakishly small.

It’s a weird perspective illusion, at least, but we also know how ubiquitous photoshop is, too.

The black top and shorts give the illusion those parts of her are smalller.