As part of the Britain's Got Talent tour starring every finalist from the TV competition, the concert in Glasgow came a day after runner-up Boyle canceled her two performances in Manchester because of a need to rest, it was announced.
But Monday night she wowed 6,000 fans, as Boyle, 48, sang her renditions of "I Dreamed a Dream" and "Memory" and sparked spontaneous applause, according to her publicist.
"Halfway through the first song they were on their feet giving her a standing ovation, and they remained on their feet the whole way through," the rep tells PEOPLE.
"They were cheering her on. And she was ecstatic with the performance. She was really, really happy with how it went. "
Boyle, the spokesperson adds, is "doing what she loves doing best, and that's singing."
Rest Is VitalHer brother John wasn't at the show – he hopes to catch his sister in Edinburgh – but, from photos he has seen, says it is obvious that she is "enjoying herself." Adding that 95 percent of his sister's fan mail comes from the U.S., John Boyle tells PEOPLE: "I just want her to be happy and enjoy herself and sing. At the end of the day, it's the quality of her voice that's got her this far."
Promoters are being careful not to push Boyle. After placing second in the Britain's Got Talent final, the Scottish singing sensation was hospitalized with exhaustion for four days.
About a week later, she met with producers from Simon Cowell's Syco label at Sony and began to choose tracks for the album of her dreams. She and producers hope it will be out by Christmas.
"She has a vast musical knowledge that she is bringing to the discussions," a source tells PEOPLE. But, again, she will not be rushed.
"It is one thing at a time, and first it is the tour," says someone close to Boyle. "Then she can move on to the album when she is ready."