Transfer From Durmstrang; A Harry Potter Fanfic

Anna Fehlter is a German girl from the wizarding school Durmstrang. Even though the school is known for being masculine, there are still a few girls who attended the school. Anna is part of a new transfer program, and will be attending Hogwarts since she is the top student of Durmstrang in 1973, and 13 years of age.
She is a proud Atticus, house mascot is a Thestral, colors green and black. Atticus is very much like Slytherin but with Gryffindor-like tendencies.
Anna goes to Hogwarts as a third year during the third year of the Marauders, Severus Snape, and Lily Evans. She also goes to school with Second year Regulus Black and Seventh year Lucius Malfoy and Narcissa Black, cousin of Sirius and Regulus Black.

When young Fehlter meets these people, how do friendships and enemies come to be, and who will they be?
What things may change in the Harry Potter storyline just by there being a transfer student?

((This story was inspired by "Severus Snape and the Marauders" by Broad Strokes on YouTube, even though it's story is a far cry from the inspiration.))