I've finally mastered this!
If I watch her going one way, then scroll down a bit so the upper half of her body is missing for a couple of seconds, then go up again, she changes direction. And it keeps working!
Does the fact that she's spinning slowly on this pc make a difference? Maybe my brain needs time to catch up.
Whatever the reason, I feel very powerful!
Quick update: the above only works for me when she's turning slowly. I can't do it now she's going faster. I no longer feel powerful.
And now I've taken to turning my head round in circles in an attempt to make her go the other way - also doesn't work btw. Must stop now before people think I'm insane.