Not to mention, that she was extremely shy and kind, with a big thirst for knowledge. He had no idea how to find her without conventional magic, nor could he leave his sister alone at Castle Black. He would trust the Free Folk with any other task but this. They disliked and distrusted Shireen because of her Greyscale. If sending a zealous dark seer eager to prove herself along with the last leal men from House Baratheon would give her the biggest chance to be found, then he would gladly do so, despite his distaste.