If the Unknown Nevarran Ambassador is "only" seventy-third in line for the Nevarran Throne, then how far or close is Cassandra? She's obviously a Pentaghast so she could be a little closer to the Royal Ruling Line.
Now that I think about it, what happened to her parents? In Dawn of the Seeker she was living in a small village with her older brother, Anthony, and Uncle. Does that mean she was an orphan?
We know that she is a distant cousin to the king of Nevarra (old Markus). Going by what that means usually (it change from place to place), she could be a 2nd cousin or farther away. She could be very close to the throne or very far away depending how much the Pantaghasts have in commons with rabbits.
As for her village, the Pentaghasts are hunters. Their ancestral home is called Hunter Fell (and I'm going to joke that their moto is Dragons are coming), so I can see them actually living in hunting villages and not castles in the hunting seasons.
There is one comment to Byron in DoTS, along with the brother fixation, that make me think Cassandra never had a father. She tell Byron that she would be proud to have him as a father (*sniff*).