You're right. None of us knows. But Occam's razor still applies. There is a straightforward path to explain all of it. We have a religious conservative young morman. He is the star athlete at a conservative catholic school, in a very traditional football program. The imaginary girl friend was probably created, with the aid of friends, to help him deflect questions about his personal life, that he didn't want people asking, and certainly was not ready to answer. It became an issue when he started getting national press. Which is when she "died".