Nicole Alexander, 15, was ecstatic when she received a text message telling her she was through to the next stage of auditions for the TV talent show.
But when she arrived at the SECC yesterday morning, she discovered the message was a fake.
BGT representatives said her name was not on the list and staff said no text messages were sent to entrants.
Nicole, a fourth year pupil at St Paul's High school in Pollok, said: "I'm totally devastated.
"I've been looking forward to this since December and have spent ages preparing.
"I told all my friends that I had got through, and now I have to tell them I didn't.
"It's really embarrassing."
Her father, Paul Feeney, said: "It's terrible. We got her new clothes, her hair done and brought the whole family down to see her, only to be told she wasn't on any list and no text messages had been sent out.
"She has a new phone and so didn't have the text to show them, but we saw it, she showed us all when she got it."
A Britain's Got Talent spokeswoman said: "Successful acts are always contacted via a telephone call and not via text.
"In the case of acts under 18, we call their parent or guardian."
Nicole originally auditioned in October last year, singing the Adele song, 'I Can't Make You Love Me,' and thought she had impressed the producers.
Her passion for performing started when she was six, and she now has regular singing lessons in the Swamp Creative Media Centre in Pollok.
Nicole said the experience had put her off entering similar shows.
But she insisted she won't give up on her dreams and still wants to keep singing in future.