Susan Boyle's family are convinced the hospitalized singer will be back to her best soon. Her brother, Gerry Boyle, tells PEOPLE that he spoke to his sister on Monday and she was much improved since Sunday, when she began treatment for exhaustion
"She's dying to come up to Scotland and sit down and have a wee bit of normality back in her life. She's keen to pursue her career as well. And she misses Pebbles the cat," he says. "She's on the mend, she'll be fine."
Another relative says Susan has received several "supportive messages from America."
Appearing on Tuesday's British breakfast show GMTV
, Britain's Got Talent
judge Amanda Holden said there's no reason to think Boyle has any "underlying" health difficulties.
Holden said, "I understand that we've spoken to her doctors, and they really have reassured us that there are no underlying mental issues, and it purely is just that she's knackered [tired] – for want of a better word."
She added, "I know that we care very much about Susan, and so the right people are looking after her now."
Doctors on Sunday examined Boyle, 48, after her disappointment Saturday night
, when she came in second to the dance troupe Diversity on the TV talent show that launched her. She was then taken to – and remains in – the London Priory Hospital.