Who does the movie think she is? That’s a different question than the one I started with, but it’s an interesting one in its own right, and one Trier is honest enough to leave open. If “The Worst Person in the World” is about Julie’s indecision, it’s also about Trier’s ambivalence. Some of the suspense in the film comes from wondering what he will do with her, and whether, as much as he loves her, he can figure out how to set her free.