The Forgotten Secret

Arianna is a fairy princess left hidden with a human couple named Reed and Rose Rivers when she was just a baby in the small town of Bellmont. The Fairy realm is under attack by a Dark Fairy named Alirion, who is intent on ruling over the whole realm. Alirion is temporarily captured but casts a spell on the two fairies who know about Princess Arianna's secret.
Arianna grows up living an ordinary life, not knowing about her true identity. Her secret identity is shortly forgotten. After her sixteenth birthday, she accidentally meets Caspian, a fairy from her realm, and they become special friends. Eventually, with the help of Caspian, Arianna discovers her true identity.
In the meantime, Alirion escapes and threatens the safety of the realms again. Arianna joins Caspian in the Fairy realm, along with her true family, to fight against the Dark Fairy.
Arianna's realization of her fairy lineage aids in her unlocking her hidden magic, which is the key to overcoming the said Dark Fairy. She unleashes her magic and defeats the Dark Fairy for good.
Arianna is reunited with her Fairy family but is given the chance to live with her human parents anytime she wishes. So, that is what she did.