Spellmaster of Hogwarts: Year One

Celestia Stellia is a witch... without knowing about magic. Raised by her mother on pagan ideals and old beliefs, Celestia grows up with a extensive knowledge of the oldest magicks long forsaken by magic users today. After a tragedy strikes, leaving her alone and with no supports, Celestia finds herself in a place devoid of everything she has ever known, forced to adapt to a new life. A year later, on her eleventh birthday, Celestia is greeted by a pestulent owl baring a peculiar letter. She has been invited to attend Hogwarts School of Witchcraft and Wizardry and she has more magic than she ever believed. Yet being a half blood witch born of old magic is far more strange than she knows, and adapting to a world of true magic when she's grown up embracing being different is almost as difficult to adapt to as being forced to abandon her own principles. With her peculiarities, sharp mind, and adaptability, Celestia soon thrives in her new environment, more than anyone could have expected, pushing the boundaries of magic in ways that no one anticipated.

Modern Harry Potter AU because I'm bored.