The 18-year-old had tried out for Gary Barlow and Kelly Rowland on last year's show, getting a standing ovation and glowing comments from the panel at auditions in Cardiff, but was axed at the bootcamp stages.
Chelsea, who made her big comeback on BGT at the weekend, admitted her performance suffered because of nerves, but was determined to make sure it wouldn't happen in the next stages.
“It was because it was the first time I was stepping on stage and meeting the judges," the Welsh singer explained. “I auditioned for X Factor last year but I didn’t get through and this was scarier.
“I think next time I will be better.”
Chelsea also revealed that she had originally planned to sing an Adele track, but changed her choice at the last minute.
“I have always loved Purple Rain and it was a last minute decision because I was going to sing an Adele song," she said. "Backstage someone said a contestant had already done Adele so I went for the Prince one.”