DUBLIN — The sensational Susan Boyle gave her thousands of Irish fans the thrill of their lifetimes last night when she appeared onstage at the O2 Center in Dublin.

Even crowds entering the Docklands arena weren't sure if Boyle would show, or be a no-show — as she has had to skip a few of the "Britain's Got Talent" live concerts because of exhaustion.

"We really had no idea if we'd even see her," said Kelly Fay of Drogheda. "We just were hoping and praying. She was the only one we came to see."

To deafening applause, Boyle came onstage around 9 p.m. and smiled to the standing ovation that greeted her.

In a few seconds, the familiar music from Andrew Lloyd Webber's hit Broadway musical "Cats" started playing, and Boyle  began "Memories." The song, which seems simple and sentimental, marks a somber and dramatic moment in the show, and is notoriously challenging even for singers of long training and experience.

In fact, Boyle herself had a nervous moment of hesitation in her "BGT" semi-final performance, but quickly made up ground and flexed her voice to bring the judges and the TV show audience to their feet.

Last night, she did the same at O2 Center — but without the opening nervousness. The crowd loved it, and were still cheering and shouting her name when everyone's favorite Susan Boyle song — and the one that launched her into superstardom — began.

"I Dreamed a Dream," which almost seems to tell Boyle's own story of yearning for what seemed impossible, brought the songstress right back into form, pitching and diving through the acrobatic and demanding music from the Broadway classic "Les Miserables" like a pro.

Cheers and applause interrupted the performance several times, but Boyle stayed on track to the climactic finale, which brought the house down with cheers and shouts of "SuBo!" from the crowd.

Illuminated from every angle by spotlights, Boyle spread her arms wide, as if to embrace her thousands of cheering Irish fans.

"She looked great," said a thrilled audience member.

"She was only onstage for about ten minutes, but they were ten minutes I'll never forget," said a young woman named Meghan. "I loved every second."

Boyle's spokeswoman seemed happy as well, saying only that "Susan has missed some shows on the tour, but is delighted to be in Ireland.”

The overnight sensation had been staying at the Morgan Hotel in Temple Bar,  where fans and photographers awaited a glimpse of her before her journey down to the O2.

The "BGT" live tour features all the finalists from the TV show, including the dance troupe Diversity, which shocked Boyle's legion of worldwide fans by winning the competition.

From Dublin, the show moves on to Belfast — another place that is very definitely friendly country for Boyle.

Boyle is clearly the main attraction of the show for Irish fans, who have been lighting candles in churches in Dublin for her.

In Donegal, Nancy Sharron, 54, said she would boycott the concert if Boyle did not appear.

"The only reason I bought a ticket was to see Susan," she said.

"She has become such an inspiration for lonely women."

"She's come out of absolutely nowhere and blown everyone else off the stage.

"The organizers should make sure she is well enough to perform but if she's not singing, I'm not going. I've no interest in seeing a bunch of teenagers with their whole lives ahead of them. I want to see this woman who was written off by everyone and then stunned the world."