I think she's old enough to listen to the tunes at Taylor's Traditional Tunebook and find ones that she loves. When I was her age all I had was a piano book of world music - and I dogeared all the pages with Irish tunes. If I had had the Internet...who knows...

Once she finds tunes she loves, you can find notation, recordings, history, etc. all over the net. She would probably also enjoy jamming with the adults. Eleven really is an impressionable age - strike while the iron's hot!