Bellucci, a 21-year-old junior at the University of Delaware, had front-row seats at the singer's concert with her sister, Allie Bellucci, 24. In video captured by Allie, Buble can be seen asking the crowd their favorite shower songs.
Allie and Erin jumped to get Buble's attention, and a flustered Erin told Buble her go-to is Etta James' "At Last."
"Ask her to sing it," shouted Allie.
Erin waved her sister off, but Buble wouldn't be deterred, giving Erin the mic.
And boy, did she deliver.
"That was so beautiful," said a stunned Buble. "That might not be your last time here. That was incredible."
Erin told Inside Edition she's "over the moon" about his response. "I don't think I'll stop smiling about it," she said. "... It just felt like this is what I'm supposed to be doing right now."
For her part, Allie is glad she made her sister perform. "She looked back at me all nervous, and then the piano started and she was ... a star," Allie said with a laugh.
Erin is studying music and hopes to one day teach children.