I don't remember much except that in occured during Entropy . Spike and Anya become Spike ,Anya and Buffy . maybe Buffy joined during the act in the magic shop ,can't really remember . please help . I do remember that the authour 90% had her own site though.

It's Maryperk's Nothing Wrong and its sequel Ready, you can find them in her website Wicked Temptation and AO3.