I think she's the act that could make the most money - her voice is incredible for her age, and I'm sure wth some maturing and more training, she could be up there with the best of the best.
That being said - I'm sick of singing acts. I don't understand why they don't just go on the X-Factor, unless they feel the competition is too strong on there surrounded by many other singers. I like BGT for the variety, and singing isn't the only talent out there. Probably the one that makes the most money, but that shouldn't be what competitions like this are about.