Grace VanderWaal Talks 'AGT Holiday Spectacular,' Advice to Young Singers and Her Weirdest Song

"America's Got Talent" season 11 winner Grace VanderWaal dishes on the series' Holiday Spectacular (Monday, December 18 at 8 PM ET on NBC), her advice to young singers and the weirdest thing she's ever written a song about. Interview by XFINITY Senior Entertainment Editor David Onda