Singer-songwriter Sabrina Carpenter seems to have exploded on the music scene, but her path to the top of the pop charts started more than a decade ago, posting videos on Youtube. And now, her latest album, “Short n’ Sweet,” debuted at #1. Correspondent Tracy Smith met with Carpenter during rehearsals of her stage show to talk about how the shutting of her Broadway show “Mean Girls” was a blessing in disguise; casting her boyfriend Barry Keoghan in the music video for her hit “Please Please Please”; and crediting her family (and caffeine) for the ability to deal with success.