I think that is:
All Too Human by Margot Le FayeIt's part of the Primal Dreams series.
http://pages.prodigy.net/leighschneider/ath_1.htmI don't recall if Willow and Xander were vamps in it. There is another story along similar lines but completely different (if you know what I mean) by Laure Alexander in which Angel is not dusted but Willow and Xander are vamped:
Lily by Laure Alexander (which starts the series)
http://www.meanderingmuse.com/lily1.htmlfollowed by the story that reminds me of your search:
Moments in Time series by Laure Alexander
http://www.meanderingmuse.com/crescent.htmlI hope one of these series is what you were looking for. If not, then I don't have a clue.
