Here's Wagner's statement.
"I’ve truly relished working with my longtime partner Tom Cruise to revitalize United Artists, and I am proud of all that we’ve accomplished in the past two years, reinvigorating the brand and developing such a strong slate of films," she said. "But I always tell my sons, ‘Follow your passion’ — and I’ve got to follow that advice myself. As much as I’ve enjoyed my time as an executive, I have longed to return to my true love, which is making movies, so that’s what I’ve decided to do. I still believe in our vision for UA, and I am confident that Harry Sloan and our colleagues at MGM will see that vision through to reality."Here's the reporting on the issue
Paula Wagner leaves UA (Variety)
Paula Wagner departs United Artists studio (Hollywood Reporter via Reuters)