Long Lost Half Sisters

When a girl named Callie Castle shows up at the Salvatore boarding school things get a bit messy. Callie starts to make friends and she becomes part of the group. But Callie has a secret that nobody knew but throughout her time at the school she starts to show signs that she's hiding something from everyone else.

During her time there a couple new kids join the school and they as well join the group. They become really close with Callie and they're the first ones to notice. Nobody says anything but they all watch her. They do research and they find something that leads them to a clue to a person that was once an enemy of the Mikaelson family.

Slowly as time goes by and they become impatient and they confront her.

What happens when Callie's secret is revealed?
Will they still want her at the school?
Will they have to put their life on the line to protect her and her secret?
What do you think Callie's secret is?
What will happen when the Mikaelson family finds out?
And what will happen when her family past is revealed?