Weird. Can you describe what happens when you click & drag?
Ok, thank you for the hint - I figured it out now. You have to click and hold the ruler, then drag the mouse away to the side (the ruler won't follow the mouse), then release the button to get a smack.
You have to drag the mouse to the same side you are on. So either from her left buttock to the left, or from her right buttock to the right.
Let's just say that this was _not_ intuitive for me...