She had not expected to hit him, so the result was entirely what she had expected. Her entire purpose was to move, unhindered, while he was busy defending against her attack. That is, as unhindered as one could be, dragging their feet through the muck of the swamp. The mud and muck slowed them both down.
Once the needles were blocked, Zelos pulled back his whip. Was she always this fast? No, not that he could recall. Even with the swamp slowing her down, he was certain she was moving faster than she ever had before.