Northmen no, but that doesn't mean she doesn't deserve the check. In this game, knights are shaped by their actions, and someone who may be trying to be kind and gentle can find themselves forced into the role of a cruel tyrant, albeit reluctantly. Such things are a recurring theme of the Arthur saga.
Irish knights, ostensibly, are bound, and just as loosely, by the same customs Cymric knights are. But this sort of this has almost as much to do with reputation as character.
For example, it would have been merciful to offer the knights a chance to surrender, and I would have declared a Merciful check in that case.