Because Yita, who was still clashing with Revenge Shadow Rider, had completely transitioned from a half-offensive and half-defensive state to a defensive one, she could parry one strike, and then a second, a third, a fourth. The attacks from Revenge Shadow Rider grew faster and more ferocious with each hit, the black blade cleaved to her as if it were glued on, and no matter how she twisted and turned, she couldn't shake it off.
Yita was panicking now, as she seemed to have just grasped what humans refer to as "panic." Perhaps her understanding wasn't entirely accurate—if expressed in her elementary vocabulary, it would be that you can't control your own rhythm. Even if the data mentioned it, even if you've practiced it hundreds or thousands of times in mock battles, once real combat starts, the level you can perform at isn't under your control. Moreover, she hadn't yet grasped how to handle Revenge Shadow Rider's dual blade suppression.