Found something that might not be what it's supposed to be:
After the Moths Reign fall during a war with the Goblins Reign, if in the daytime I enter the moth forest and choose "fast travel", I find myself near a moth gatekeeper... and after I making him fall a sleep (or sneak past him, if he sleeps already) I reached chamber of the Moth Princess, while she sleeps inside (while in fact she is already in my squad).
Otherwise, if I do not "fast travel" through the forest (or "fast travel" but during night time) I get to the Goblin Ambassador.