Now- I'm going to ask a semi-stupid question...
How many feeding aspects do you think the WCVamp can place here? I mean... really.
The semi-stupid part is "Duh. Infinite, limited only by the creativity of the player...." but I'm not so sure- at least, not in the crews I run with. It's considered bad form if not outright double-dipping to place 2 nearly identical aspects on a target. For example, if a teammate uses a sudden flare of light to leave a target "Blinded by the light," and then I throw sand in their eyes to leave them "Blind as a bat," my GM would smack me. And when I GM, I would smack any player who similarly tried that. Blind is a nearly binary trait- you either are or you aren't... you can't be extra-blind. (note, I said nearly. One can have severely hampered vision, but that's still not a lesser state of blindness).
(Best case scenario on that one, I'd allow the second maneuver to extend the duration of the first).
If that leaves you unsatisfied, now imagine that the next player in the order comes up with a knife and slashes the target's face, makes a phenomenal roll, and leaves the target with an extreme consequence aspect of "Eyeless." Have we reached the limit here, or can someone come along to make him even more blind?
That said, unless the WCVamp is one of those rare (indeed, unheard of in the books) ones that can feed off more than one emotion simultaneously (which you have to pay extra for in the mechanics, in which case I have no problem with the idea)... then you're running into that same problem- multiple aspects in this case are going to be layering the same emotion on top of itself...
There's something to be said for shoring that emotion up, making it more powerful... but that's more about it being harder to resist than it providing a better damage bonus... and even if you represent it with multiple aspects, there ought to be a limit to how much stacking can occur like this (specifically, identical or nearly identical aspect stacking) that might prevent the problem you're talking about.
Or you could simply rule that using Emotional Vampire is a tag of that aspect, and that way, even applying one every round, they can't gain their +2 without FPs.