Nope, it's definitely not random, 'cause I just figured out accidentally a way to make her switch at will. Someone else linked me to this so I did it again and ended up doing this:

My monitor is however far away from my face, maybe like a foot and a half or something. Anyway how I did it was to like, put both my hands together like I was praying and then make a gun shape with my hands, you all know what I mean. and then I had my fingers lined up with the woman on screen but so I could still see most over her as well. Then I focused on my fingers so she was just out of focus in the background, and then rotated my fingers clockwise or anticlockwise, and if you keep it so you can only see her out of focus, you can pretty much change her direction at will (I can, anyway.) I can get her to turn back and forth mid spin and everything

edit: heh, don't even have to make it that complicated, just stare right at her and then move one of your hands in front of your face clockwise or counterclockwise and you can get her to change