You are so beautiful, (like) tall grasses, plum trees.

Speak in my voice hereon

And no-one will ever question ye.

Mophei tries to cure Kay's stutter, which she developed through emotional trauma. But Kay likes herself flawed and prefers herself - by now - dragging many crosses. Later he inadvertently fixes her eye and by the last chapter, Kay loses the stutter almost entirely. You can just tell, by her dialogue with Snufkin in the last page, that she's going to get herself in trouble in no time, as soon as you close the book.