WELL UH...Ranmaru despite her love of fighting doesn't actually want to hurt anyone in this kind of context. It wouldn't feel right to her.

That's why I'm gonna have her attacked by Goblins and forced to defend herself, at which point she'll be dragged into fighting on the side of Humans just by virtue of that. She won't be happy about it though. She's also available for useless attempts at trying to talk other people down if they're really going at it to hurt anyone (humans or goblins.)