(First, I hope she's never actually been raped.) I'm a guy, not a girl - I usually prefer face-to-face positions, but sometimes I just feel an urge to use a willing, faceless partner for my pleasure alone. Some girls like the rear-entry positions (doggy, spoon, etc) for the same reasons - they don't have to look at the guy, and they know he can't see their face.

(Other reasons guys like them are: they can watch their erection slide in and out, and a lady's upturned backside is just sexy to look at - always reminds me of a valentine heart being offered to me. Girls like them because the guy can go pretty deep, which may be good or bad depending on the physiological details of the two people involved.)