Here's a poor imitation of Malenia's Waterfowl Dance. After spending hours making this animation I realized she does 2-3 slashes instead of just one so it doesn't look as good as the original masterpiece.
Image below contains SPOILERS for the new boss.
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Also it's not Regina as implied in the post below. Her name is Mena. After getting her ass kicked by stronger version Hailey she came back in to eliminate when she was weak.