How about this? Why can't we just say that Kat is Kat? She's from a fictional universe where our nationalities may not necessarily apply. Her having darker skin may not mean anything to the people of that universe. Also, I don't think Kat's nationality has ever been stated by the creative team.
Kat is Kat, leave it at that.
the only reason i choose to believe this is because you rhymed at the end