Disclaimer: I do not own these characters and I do not claim to.
It makes sense.
It makes a weird, confusing, messed up sort of sense, but there is still sense to be had there, somewhere in the craziness. But, hey, that's like the rest of her life.
There were, of course, those couple of days after she realised, really realised, what it was like back when between Spike and Angel. Those days where that certain nightmare came back and took a starring role in her dreams and filled her back up with anxiety and jealousy. Mostly jealousy. Because how could she compete with that? Because they'd been together for twenty years before she'd even existed, because they'd known each other for over a century, because they were two of a kind.
"Yeah, well," said Spike, wiping away a streak of blood left by their current (but fortunately late) mystery monster, "in a hundred-thirty odd years, Angel and I've only ever agreed on one thing."
"You, Buffy," said Angel.
And then she laughed so hard that Angel had to grab her before she fell over because she had just spent the last ten minutes watching them fight in perfect tandem and because Spike's a big dumb liar and she loves him and his blustery bullshit and because Angel's so cheesy she can't believe she used to think he came up with his lines on the spot and because they're both so perfect for each other and for her than she can't believe she spend so long thinking otherwise.
And then she pulled them both to her, demon blood and all, and hugged them together despite them both insisting that they 'didn't do that'. "I love you both too."