Hi!
I'm not entirely sure about the plot before but I think Buffy is in her late 40s or maybe even in her early 50s and Willos gives her a little gift. Buffy then visits various alternative universes/dimensions.
In the first chapter, she and Spike are at the beach; it's somewhere post-S4 or maybe early S5. Spike is still soulles but both of them are together and very happy. Buffy then learns that AU-Buffy has given up her slaying duties and 'normal Buffy', in her body, assumes that Faith now has a 'new baby sister' called Dawn.
The second chapter plays in a world where Buffy and Riley eventually got married and had two kids (a boy and a girl, I think). However, she and Spike are having a secret affair. Riley catches them at the end and I think either Riley or Spike get killed.
The last chapter I had read plays in a world where Spike didn't merely attempt the rape in SR but actually raped Buffy. Although this led him to get a soul nevertheless, there were huge trust issues between Buffy and Spike so he didn't get to wear the amulet Angel gave Buffy in Chosen. Faith and Spike are a couple (I think) and the First and Ubervamps have taken over Sunnydale/the world.
This is all I can remember - I'd be thankful I someone knew what fic I am talking about because I know I absolutely LOVED it. | 
