Almost sad these 'conservatives' grew up in such hate that a grandparent never called them a nickname based on their name but changed slightly over years. which is probably all this "name" is...
Fin is a logical shortening of Seraphina. The poor kid does not deserve to be attacked for merely speaking at their grandfather's funeral. They might be trans, they might not be, but this has "forcing someone out of the closet" vibes. We don't need to guess, we can just wait until Fin tells us.