[She took a deep breath and held it for a moment before letting it whoosh out.] You decided...you thought that we--it was like...our time or whatever. [She's not going to mention the whole Twilight thing to him. That's too much, too weird and too close and not related to why they can't be together at all. Sure, it'd been kind of a crazy thing, but not ultimately why they couldn't have a relationship.] I...yeah and so we did. The whole...together thing. Together. [Special emphasis and some very direct staring before looking back down at her feet.]
The world ended. Or rather the barriers between hell dimensions and our world fell. Demons tore it apart and we created this little...paradise that was just me and you. Somehow. I took it back. I undid it all and it cost the world every bit of magic left in it to do it.
[She paused a second.] You were sort of upset, went evil and [very quietly] killed Giles