The gif means nothing. If you play the frame sequence backwards it goes the other way. I've had two instances of the same image open in two windows spinning two different ways.
Did you consider that maybe, the very act of looking over to the other image, or having two of them run at once, disorients your vision enough to break the trick, and then perceive it the other way?
I can make the woman change direction at will now, but I can't do it with the cat. I originally stared at it for quite a while and didn't get it, then managed it.
A big part of it really is what frame you start paying attention on, that'll decide what direction your brain is spinning it. Its also why focusing on just one feature helps change it.
I saw a green square where the cat should have been for a moment before it changed direction, right after loading the image.
…because its a gif being dropped onto a static background?