She's got a sword! That's alright we all got swords!

Jokes aside the marines do have a swordsman but I don't think that's a problem. And just to check. She's 12 feet tall? Cause I mean that's fine, it's just a little surprising, is she part giant or something? XD Either way its fine, this is One Piece and we have people like Whitebeard walking around that are like 5x as big as normal people.