The I'd Do Anything winner, who is currently helping Webber with his search for Toto, argued that the West End composer had succeeded in his "vision of bringing live theatre" back to the mainstream.
"I was so chuffed to hear that Andrew was doing another [TV talent] show. I'm a great supporter of these programmes," she told DS.
"I tried for years to get to the West End. And the Nancy show finally gave me that chance. The programmes showcase so much talent, open so many doors, they fund massive singing events around the country, they fund people through college and most importantly bring a whole new audience to the West End.
"There is that stigma about it being a reality TV show, but I can't tell you how many people have come to me and said, 'Oh this is the first musical I've ever seen. I want to see another one'. I mean how brilliant is that?"
She continued: "The [I'd Do Anything] Nancys have all gone on to star in things like Wicked, Les Mis and Sister Act. It goes on and on. That's why these shows are brilliant. Because it isn't just about the winning act. So many positive things come out of these shows. That's why it angers me when some people get bitchy about them.
"I think in Andrew's case, he did have a vision of bringing live theatre back. And I think it's great how they do fund people to go to drama school and put these live events on around the UK. It's not just about who wins on a Saturday night. I just love the whole thing, I could speak all day about it."
The Over The Rainbow final will air on Saturday at 7pm on BBC One.