Once upon a Hogwarts

A 14 year old girl Y/n Diggory, sister of Cedric Diggory is joining a 4th year at Hogwarts. Why did she join now and not before? These thoughts crept into the minds of most of the students at Hogwarts. She soon get very interesting for all, but especially to two slytherins, Draco Malfoy and Peter Pan...