At the reception, Diana sang "Endless Love" to Ashlee and Evan in a very special once-in-a-lifetime moment.
Ashlee and Evan went public with their relationship in July 2013, and things quickly got serious between the two, with Evan calling Ashlee "the One" last November at the Los Angeles premiere of The Hunger Games: Catching Fire.
"Yeah, she's the one," he told The Insider. "It's amazing. I'm so in love and we've got amazing things going on. And we inspire each other. So it's cool."