[ Saying that he doesn't care at all would be the lie of the century. He does, about her and Buffy and far too many others and that bothers him to such a degree that he needs to pretend that it's not true for no one's sake but his own. Of course he doesn't care. They can burn in hell as far as he's concerned. He's the Big Bad for crying out loud!
There's something satisfying about watching her walk away. A small victory, perhaps. There you go, Spike. One more tentative bond severed. You don't want to go down that path. ]
Good, that's exactly what I want! Now stay the hell out of my soddin' business!