She is not stopping and turning you are seeing her one way and then your brain is seeing her go the other. It is an optical illusion and how you look at her is what determines what you see. So if you see her go both ways you are using both sides of your brain not just one. Those who are only right brained will only see her go that direction. Or left as the case may be.
I see her go one way and then if I think about it I can see her going the other way. If you can see both directions try thinking about seeing her go one way and by thinking about it you can make her turn the other way. It is in how your brain is perceiving the image.
I enjoyed this!! I love optical illusions.