It would seem that the simplest answer would be known by the person that was with her last - Joran.
That is not necessarily a true statement. It has a little spin on it. Just because he was the last known person to be with her or to see her doesn't mean he knows what happened to her. I thought this thread was about finding the simplest solution.
Back to the same old she said, he said, she did, he did argument that every thread appears to end up with. Derailed again, eh?