Grace sings a live duet with Shawn Mendes via the Smule app, presumably to promote the "Singing with LG" competition. (Grace's father, was head of marketing for LG USA at the time)
Grace had recently received a guitar as a gift from Shawn.
Teen Vogue wrote: "Shawn Mendes can play a guitar like no other, and now he's going to be teaching his friends how to play, too.
And his first pupil? None other than Grace VanderWaal... She now owns a gorgeous guitar with her signature motto “Miracles do happen” engraved upon the front, a gift from Shawn himself.
Grace... took to Twitter to publicly thank Shawn for the gift. In a video, Grace shows off her new six-string, writing, “@ShawnMendes thank you sooooooo much for this beautiful guitar. It was fun singing with you today on @smule.” Shawn wrote back, promising to help Grace learn to play, saying that she’ll be strumming along in no time at all. (TeenVogue nov 30 2016)