Chris Willman Senior Music Writer and Chief Music Critic Celine Dion, who has been out of sight dealing with a serious illness, is suddenly coming out in public in Las Vegas again — including an appearance as an audience member Saturday on the final night of Katy Perry‘s residency at the Resorts World Theatre, where Dion had to call off her own engagement two years ago. The sight of Dion in the crowd for Perry’s swan song managed to get even more attention than the attendance of Prince Harry and Meghan Markle.