She performed her cover of Wild Horses by the Rolling Stones on America's Got Talent: The Champions on Monday night.
Boyle received the show's highest accolade when judge Mel B pressed her golden buzzer to put the singer straight through to the finals.
The Spice Girls star described Boyle's voice as "angelic".
"What an absolute honour and pleasure it is to be sitting here and listening to you and your angelic voice," she said.
"And I want to be the woman who gives you something you deserve," she added, before pressing the buzzer.
