It didn't happen so quickly as your put it here. There was dialogue between the two, along with Nicodemus twisting his shoulders and hurting her arm. During the time she was put on her knee's, and the time he kicked her knee it's believable, and likely that she had gotten up, or was partially up when the kick happened.
It didn't happen quickly, because Nic didn't want it to... That simple, he was talking her conversationally, like he wasn't exerting himself in the least, and he wasn't, he let her know that
as well, kind of twisting the knife, rubbing salt in the wounds as he made them you might say. Once the Sword was broken, which was his first goal, again if she was shot in the belly, how did she manage to get the Sword to his throat? Nic allowed her to, he did the complete surrender thing, trying to kill him with the Sword at that point would get it broken... Task done..
Goal number 2, he wanted to break her.. Not just her body, which he did quite easily, but her mind and spirit as well... It remains to be seen how severe or permanent a job he did do.. It was never his goal to kill her.