Different strokes for different folks. I had two girlfriends, and incidentally they were both nurses, who enjoyed the same thing as you describe, though one was more inclined just to want to get slapped and thrown around, the other one was really into the darker side of getting beaten up and worked over which it did turn her on, and I will attest to that for sure, though I don't pretend to fully understand the dynamics that make that work for her. She always worried me a little bit, though now, I wouldn't mind see her taking a brutalizing for the team. Both of them were into having other women beat them up.
On the flip side of that I have had girlfriends who would have found wanting to get beaten up seriously warped and not like the idea of getting scratch on their bodies let alone a fist.
I believe it may come down to how one is brought up, and the experiences that one has had that would make one feel sexually aroused by being beaten up... I would say that some people like you definitely find arousal with getting beaten up, or truly wanting to and probably a lot of women do not readily admit it, because they are maybe too worried, as usual, of what other people may think, or even in consideration of their safety? My question back to you is why certain women who are into being beaten want other women to beat them up? The only thing I can guess is that it is more humiliating for them and they like that? Maybe there is no one answer, or it is different for everyone. We do hear you how ever it works!
