User blog comment:SibunaSeason34/Nina Martin: What REALLY happened to her parents?/@comment-7561418-20140810131520

I'm willing to bet that Sarah knew Nina's name because she had some sorr of dream/vision that told her.

But as for Nina's parents (am I detecting a harry potter idea here), maybe it was just a coincidence,  or maybe they actually did need to be out of the way in order for Nina to fulfill her "Chosen One" destiny.