Katherine is still a badass vampire. She was kicking ass and kiling people before Elena figured out she could throw a punch. Katherine alone could probably take down a handful of werewolves and has little worried to be scared even if she's outnumbered by vampires.
Plus, unlike Damon and Stefan, she has her massive sex appeal to distract. As we've seen in the past, guys want to kiss her more than they want to kill her
