The Girl Who Lived In Three Castles

In a world where Vernon Dursley has a friend in low places and Dumbledore is...competent but busy putting out fires in the wake of Voldemort's defeat, Harriet Potter gets put into an illegal adoption 'agency' on the continent. Join her as she grows up, goes off to Durmstrang, and discovers that the Potter name looms large even when you don't know it's your name.