Jacky
Why don't you check out the site for the National Youth Choirs
http://www.nycgb.net/They have a Northern Girls' Choir (aged 11+) to train young singers like your daughter. This is an excellent organisation, employing high-quality, professional coaches who will have the interest of your daughter's voice at heart. She'll learn much about singing (if accepted), have a great time socially, and be linked into an organisation that could sustain her vocal work until she's out of University if you want.
I agree with others about not pushing a young voice too hard too soon. NYC doesn't do that. It's quite hard to get in, which will also give you a feel as to how your daughter compares with others of her age, but if she made it I think she'd have a wonderful time. Quite a few of my pupils are involved in the organisation (at various different levels) and absolutely adore every minute of their courses. They meet in the holidays on the whole.
Worth a look - I warmly endorse it as a route for young singers.