Susan Boyle, the frumpy Scottish spinster whose amazing voice has become a global YouTube sensation, stunned audiences again on Sunday as she was voted through to the final of “Britain's Got Talent.” Singing “Memory” from the musical “Cats,” the 48-year-old overcame initial nerves to produce another command performance, her soaring rendition winning the telephone vote on the talent show. Wearing a shimmering purple dress, Boyle looked far more primped and preened than she did on first appearance on the show last month. This time, her hair was coiffed, her eyebrows were plucked and she looked almost every inch a star in the making. After her performance on Sunday, Cowell was moved to apologize to Boyle, saying she had been poorly underestimated. “You know what, I just want to apologize because of the way we treated you before you sang the first time,” he said. “You made me and everyone else look very stupid and I'm very happy for you, very proud for you.” In Sunday's semi-final, Boyle defeated seven other acts and will be joined by Diversity, a troupe of street dancers who came second on Sunday, and two other acts yet to be decided. The winner will perform at the Royal Variety Show and receive a check for 100,000 pounds ($159,000).