Directed to Redsonga as per our previous discussion, hehe, I was just thinking something. The Labryinth fantasy story comes from the book Sarah was reading at the beginning of the movie. That's where it all originates from. And the line "You have no power over me" is
in the story, it's not something Sarah added later on in order to break the fantasy. It's
part of the fantasy, it's the way the book is supposed to end. It allows her to stand up for herself in the end (but also always keep a part of her childhood close
).
So in that way, that line doesn't contradict or ruin the story at all, it's how the story was meant to be ended.