How WOULD it go in a Harry Potter world? Would it even get to that point? I think in the HP world, Cassandra just have to disappear for a few centuries and then the wizarding world would forget all about her after dealing with the periodic Dark Lords and Dark Ladies. She'd have a problem every time they realize what her powers are all over again though. She'd probably be able to find someone in Knockaturn Alley who could remove the tag, assuming she could learn enough about the wizarding world.