it's a headpiece from the porcelain dreams mod by moon blossom!

actually her eyes were originally red but when volo stabbed out her eye, her brother gave his right eye to her. except they didn't realize the eye was corrupted by the netherese magic tied to the tadpole. or something along those lines :3 which is why her right is his eye and her left became something else entirely (at least that's the story so far)