The amusing interview with her is followed by archival footage of Frankie (on top of the world, ma!) performing "Saturday Night (Is the Loneliest Night of the Week)." Frank is actually performing with Harry James, and not Tommy Dorsey, as is implied in the preceding interview.
In 1939, James "discovered" Sinatra, who at the time was working as a singing waiter at the Rustic Cabin in New Jersey. James hired him on the spot to be his big band's singer.