Is it okay to sing a Carrie Underwood song for American Idol?

I just turned sixteen, and I am auditioning for American Idol in a few weeks. I really want to sing Undo It by Carrie Underwood, and I don't sound anything like her when I sing. Everyone tells me I sound like Dolly Parton. I was wondering if it was okay to sing one of her songs since she won the show? I didn't know whether it was a good choice or not. =]