Non-mortal magic isn't subject to the laws, but a warden may still lop the casters head off if they aren't protected by the accords.
I was considering this the other day, and I think that Lawbreaker is just as applicable to vampires... provided that they are breaking the Laws in regards to other vampires. After all, a mortal gets a pass on the Laws if he or she breaks them in regards to an animal, a vampire, or some other monster, so why wouldn't a vampire get a pass for the vice versa?
So, if Arianna used her sorcery to kill a mortal, it wouldn't be any different than if Harry used his magic to kill a deer. However, if Arianna used her magic against Thomas or Mavra (or at least another Red), a fellow vampire, it would earn her Lawbreaker (First). Fortunately for her, there are no Wardens of the Red Court, so no one would come to cut off her head in any case. All my opinion, of course.