So, even in my *real* headcanon Felix is in charge of "Human Resources" i.e. declaring his eternal love to every secretary in turn. He promises to speak to the Three about changing her after a couple years of exemplary service. It's the Volturi's way of ensuring that people like Gianna don't blab, and that they work hard every minute of their tenure. Of course Felix always has a nice snack in the end. Demetri is completely grossed out because he doesn't see the draw.

Aro: Yes, Felix?
Felix: *slight bow* About Gianna, Master...
Aro: Is there a problem?
Felix: *sneaks peek over at Sulpicia who is standing there massaging Aro's neck* It's... rather delicate...
Aro: *holds hand out*
Felix thoughts: She's getting old... her blood is practically past its expiration date, and I'm so thirsty! Please?!
Aro: Ah, I understand, my old friend. And you are in luck; just this morning we engaged a new secretary. *Felix grins, runs out*
Demetri, in hall: Where are you off to, in such a hurry?
Felix: *holds up diamond ring* I'm proposing to Gianna, right now!
Demetri: You're disgusting.