He's also worried that the "Britain's Got Talent" media machine will change "the real person" he knew and distract her from nurturing her talent.
"It is a very good instrument, but I am concerned about her being surrounded by all these PR people that she will not be given the time to sing," he told the newspaper.
But Ruffel said the attention hasn't changed her friend at all.
"She's still Susan," she said. "She was in here the other day, and we were saying to her, 'Finally you made it.' And she said, 'I don't know what all the attention is about, I just wanted to sing."
"You won't change Susan," added Ruffel. "We have a saying here: You can take the girl out of Blackburn, but you can't take Blackburn out of the girl. She'll stay the same with her feet firmly on the ground, a sensible girl."