Have you unlock the Dark Swamp? If not, keep exploring the normal one until you do, then have a look around in there at night until you get the scene where you are running away from something chasing you in the fog, that leads to her hut unlocking.
I thought we were wandering and her voice appears in our head and we see a wisp then pass out...
I think that is how the game describes when that event happens in the Dark Swamp at night, it can be hard for me to remember things.
