Edit: Ah, I discovered the problem, and feel somewhat stupid for it. As it turns out, I was correct about there being code elsewhere overriding it, but the actual source of that is I'd made a backup of the animation file before making said changes, and had forgotten that I needed to move it out of the game folder. So my backup animation file was overriding my changes to try and make the drips and piercings work. After moving it out of the folder, things are working as expected.
Edit 2: Got everything working properly and updated the Laura_Animations.rpy file in the scripts.zip on my
earlier post.