I figured it out, turns out it was bugged, just had to restart the game to get it to work.I never had any real problems with her, but maybe that's just me.
The harpy and the mermaid both had their "hitboxes" in such a way that they never became red just orange.
Might have been something wrong with how it rigged onto their skeleton or something, making the spot actualy under the place it was sepose to be, but a restart got rid of it, so if anyone has the same problem just turn it on and of again, works every time.