Hmmm...that Kickboxer 4 sounds very similar as far as plot, and I know I've seen it. Perhaps that's the one I'm remembering. The only differences I can think of is that I'm almost sure the cute girl gets killed in her fight, gets her neck snapped after about 10 seconds. I think the other woman was a competitor as well, but I don't believe she ever fought, just ended up running around a dark loading dock with the guy.
I'm pretty sure it wasn't a Cynthia Rothkrock film, I've seen most of her movies and I don't think she was in this one. Those things can be incredibly silly cheezy fun