Mai may not be the greatest ninja ever in ninja skills, but that makes it even more of a fact that even at Mai’s ninja level, she’s MORE than capable of defeating “the strongest woman in the world”. Which goes to show even ninjas that are not OP tier can still defeat Chun Li everytime.
Ninjas are on the upper scale of the warrior food chain. kung fu masters are below that. the very nature of a ninja is to kill while avoiding detection, and even in a straight up fight, they are lethal and a force to be reckoned with. martial arts like kung fu aren’t really about killing more than self defense, but they are completely vulnerable to assassinations, and warriors like ninjas are more in sync with the art of war, they don’t limit themselves like kung fu does. ninjas are like the perfect killers.
Also add to the fact that Mai possesses fire element. Chun Li has chi/ki energy for projectiles and spheres but it’s not nearly as destructive as fire. So element wise, Mai is more powerful too.