after you become a warrior, a flower will spawn where she was for that 1 day she was sitting up there and you will say "I wonder what happend to Nightwhisper"
talk to the gray cat which is in the place next to the beach not the one at the beach listen about mosskit and get something to put on the x at the beach and if you got the correct item (which I won’t ruin it for you) come back at midnight in game and she’ll be there