I should add, as an afterthought, that even if what Fox just did was acceptable it wouldn't have stopped Shax from fighting. If anything it would have urged her on, not to mention he'd have made himself a target. After all that he'd be powerless to stop her from grabbing him by the throat and snapping his neck, or various other gristly ways she could kill somebody without her sword... And with how the character is, she'd do it too. Near-enough thoughtlessly.

Having said that, I know Shax isn't exactly good at making friends, so I'll pass over a little help. If she can be convinced that they can bring her to other fights, more than she'd find if she killed them and went on alone, you might make her consider stopping the fight before a death occurs.

Although, you'd have to keep your word or she'll end up starting a fight again.