She could mess some UFC featherweights right the fuck up, and I'd bet money on that.
If a man actually punched her full out in the face and knocked her out, the media would shred the sport. Casual fans would lose their minds. The world as we know it would implode.
That said...I am sure there are a few guys out there in her weight class that she could beat. No doubt in my mind.
Do it in Japan!
Who would take that fight? If you lose, you got best by a girl, If you win, you are a woman beater 
4l8er
I'd take her on.
That woman needs to be stopped before she seriously becomes a man