I have a degree in art and my ds12 leans heavily towards the arts...so I guess I'm a parent of at least one artist.
I mainly wanted to say that your daughter's observation about the specific quality that her work used to have is really telling that she does in fact have some basic understanding of the beauty and truth that can be expressed in art. Cool stuff.
Perfectionism, shyness around her friends, getting older, all these are factors that could be contributing to feeling constrained when making art. I don't know if advanced instruction would be the way to go.
One thing I thought when I read your post, it might help if she has her own space to really make art in private, stuff she can hang in a small room that most folks never go in. Sounds odd, maybe, but seems to me that could be pretty freeing.
Best of luck!
