It would be more than upsetting or tragic, Miss Yuuki. [ simply ]
Being on the list means that we know she's a vampire. It means we know she's capable of making other people into vampires, and Sir Weller's change in behavior and the fact that he and Mr. Archers have moved in with her might raise some flags. Being on the list means we can address this as a potential vampire problem. As I keep saying: it's a list of people who are under our jurisdiction. It's how we know who to protect and who to intercede on behalf of and, yes, who to confront, when problems arise.
And... I'm sorry, but I would also argue that Miss Diva is considerably more dangerous as a vampire than she would be if she were a human. No human, and no demon or witch for that matter, has the ability to easily change other people around them into more of themselves, much less more that are dependent upon them.