Focus on her hips and hands, and when she's facing directly to the left or the right, mentally pop the far hip and hand to the near side.

Interestingly enough, illusions like this don't faze my visual artist friends. Realistically rendering a scene requires the ability to see a 3 dimensional scene as the two-dimensional projection that actually hits your eyes, and applying that skill to an illusory 3-d image is easy for them.