The Edinburgh-born student, a former busker at the Fringe, was given a lifeline by the Black Eyed Peas frontman after coming off second best in a battle with Ruti Olajugbagbe and losing her spot on the team of Sir Tom Jones.
Will.i.Am then used his designated steal to give the 16-year-old another chance in the competition.
He had earlier admitted making a ‘big mistake’ in not turning round during Saskia’s blind audition, when she performed ‘Strong’ by London Grammar to wow the judges, telling Saskia she had an “awesome vibe.”
Saskia has twice appeared on fellow talent search show Britain’s Got Talent twice, and was the winner of the ‘Edinburgh Has Talent’ show at the age of just 12.
First Minister Nicola Sturgeon had offered her congratulations to the student, who will progress to the knockout stages as part of her new team with the rap superstar.