Slag is pretty much the same here in the USA. Cordelia even tells Buffy she looks "slagged", so the necessary confusion wouldn't ensue. What do you think of "doxy"? It's pretty old-fashioned, right? I'm on the fence. I might just stick with the original, though I'm starting to think it's too modern for Spike, who has been in the Americas at least since 1998. But, he's a guy who I imagine would keep up with the trends, especially in cutting edge insults!

Thanks for getting back to me!