With everything that had happened so far, though Seth's action of almost killing Minuha had made her snap, she was still hesitant about killing him, finding it difficult to end such a legendary specie.
With Seth thoroughly pinned down, she had let herself get carried away by her internal debate on what to do with him, and as such, she believed she had lost track of her surroundings, failing to catch when Seth moved behind her, but didn't mean she was slow to react to being sneaked upon.
No, as a woman who had made it this far in the cultivation journey, having a perfect instinctual reaction was a must for her, but in the end why was she still standing in place allowing Seth to feel her.
While Seth's lack of killing intent did help damper her instincts, the thing that held her back was the fact that Seth, or rather the Seth she had pinned down wasn't the one who had somehow escaped and moved behind her.
