Makes sense, and I think it's one of those things that's better we don't know. Nale is very much the Iago of this story; hating just to hate, with every slight real or imagined a flimsy pretext for doing so.
I lean towards the "she smells bad" theory because Belkar's goal was never to kill Miko; it was to get her to murder him and thus lose her paladin powers.