Actually, she still has her legs and arms. If you look at the top of her shoulders, you can see her hands. Also, you can notice her feets are forced up on her butt.
Why? Most of the time the people tied up are into it. Masters and slaves. This obviously being the slave. My knowledge of the whole S&M society end there, though.
Any way you look at it, something like this is going to fucking HURT, and pain like that WILL induce a physical reaction. If you're still worried about her level of involvement, though, I suppose you could always just ask her. I mean, she is right there...