Spencer Pratt, left, and Heidi Montag pose backstage at the 3rd Annual Reality TV Awards at the Avalon Hollywood, May 13, 2015, in Los Angeles. Rich Fury, Invision/Associated Press, File Facebook ...

After Sabrina Carpenter attended Olivia Rodrigo’s concert in London June 27, fans of the two singers—who were once in a rumored love triangle—speculated that they could be planning to share the stage.