The Warrior of Hogwarts

Hogwarts is said to be the safest place on earth, well besides Gringotts. The professors know otherwise. They know the threat that will rear it's ugly head. There last resort is reached. They call out to the Phoenix Council of Venus. The council sends they're best warrior, a girl named Niva, to help Albus Dumbledore out. But is there more to this girl than meets the eye? She hides a secret and a tragic past to protect the one family member she has left even of he doesn't know it. Will she tell him the truth or will he find it himself? Will she fulfill her mission in protecting Hogwarts? Or will she put her life on the line to protect her last relative?