I don’t play 2e so idk what RAW would be but personally: It’s still an encounter. Build it as such. Just instead of a combat encounter it is now possible a roleplay encounter. That lie bought time to negotiate yourself out of the fight, but having fought back will make talking yourself out of it fully harder. “Then why would you kill us”, the mitflit says as they stand there, confused but still poised to strike back if they have to. And let them continue their lie to successfully talk their way out of it. Give them advantage on their rolls. They may also choose to use the confusion to gain a surprise round and kill them if they’re more the murderhobo route.