Was she wearing an amulet when we see her at the party of William's humiliation? How old was William/Spike as a vampire? Angel was like 300? Could it be that William was made a vampire due to the vengence of a woman? A woman that he should have noticed but did not, due to Cecily? Which would mean that Cecily created the reason for the vengence to be exacted upon William, which for a vengence demon would be rather sweet. So what would have been the wish that would doom William? Perhaps... I hope you live forever and never find true love, forever being spurned. Would have worked... and certainly describes the "Fool for Love" that is Spike!