Also, while the Summer Lady being killed and her power going into the changling is a legal, as per the books. Due to the fact that the Mantle of Knight is the conscious choice of a mortal, he had to willingly agree to the bargain. Seeing as the Knight is a mortal and retains his free will, he can't be forced into it. Fae can cause other Fae to do all sorts of stuff, no free will. Fae forcing mortals... thats why they have bargains.