Oh that's not the actual reason i hate her. Tho i agree her character can be improved a bit.
My reason is much more petty than that. The reason is simple, She's the MC's love interest. Its not extreme hatred where ill be slandering her, its just that i dont like her ever since she was made luffy's love interest. In a shonen specially battle shonen like OP, i feel like romance can generally mess up stories. I just find it wierd when romance is included in shonen. And its not just in OP, i felt the same during bleach and naruto.