The white-haired hero lusting after the demon king's body is just scum.
With a hero like that, when they're fighting the demon king, they'll definitely end up fighting all the way into the bedroom, won't they!
After learning what the real pact with the white-haired one was, Shami, besides being shocked, actually let down his guard regarding the rival factions to the point of thinking about meeting the hero as the demon king, and maybe the hero would even suggest watching a movie together.
After all, the most crucial pact that led the white-haired to the path of a hero was right there. If the white-haired insisted on killing him, she'd only get his body still slightly warm.
But that wouldn't align with the pact's terms of "helping each other," or "three days and nights," now would it! It'll all be cold!
So, Shami was certain that once white hair knew his identity, at most she'd have a mental breakdown, but no real harm would come to him.