Wow. Memories.
Yeah, I was with a few different chicks that liked the rough-n-tough... hard smacking and hair pulling. I'm not into that thing, but they motivated me. I'm all about pleasing the woman, so if that's what she wants... I'll do it all night long.
Your mileage may vary. Key to success? Express your honest concerns to her as you did above, instead of just a board of horny strangers.
Good relationships are based on communication. And sometimes... hardcore ass smacking.
Talk to her!