"My father taught me two things: how to slice peoples in half and to not use it to murder peoples. Unfortunately for you, my mother taught me to disregard the second rule."

Yeah, growing up around three of the strongest "humans", two of which are your parents, she should know a thing or two on kicking ass.

It'd help explain 18 being okay with her staying on that island.

Really hope if they do a time skip they do something with her.