I enjoyed reading your post but it infuriated my 14 year old daughter. Writing stories on www.fanfiction.net is her hobby these days. I think the stories are stupid but I am glad she enjoys writing. She took the ACT in 7th grade and scored high enough in English to get state recognition.
At 14, writing fanfic is a wonderful way to learn to write. I wrote fanfic til I was about 17. The next 12 years I spent practicing writing original stuff.
Does your daughter know about National Novel Writing Month? She should look into it (google NaNoWriMo), it’s a ton of fun. I’ve done it ten years running.
One of my most valuable writing exercises was to convert my "best" fanfic into an original work for submission to a serious "young authors" sci-fi anthology. It turned out to be very instructive as to the merit of my work, or more correctly to the lack thereof. (As opposed to the quality, with which merit should not be confused.) My story was not selected for publication, which did not come as a surprise.