Walter: Fangirls are unkillable by any normal method — for humans or vampires. And no action you take will induce them to cease their obsession for you because, being taken by you, it will be seen as good.
The only way they’ve ever been removed is by getting so overjoyed with their obsession’s actions that they go into spasms of glee and pass out, losing their grip; they can then be returned to their dimension.
Seras: So basically, we have to be so ‘nifty’ that they faint from happiness at our niftiness?
Walter: And then we drop them back through the portal they entered from, yes.