You could argue that spikes attraction to buffy is there from the start, just check out him looking at her in the bronze.
As for subtext, willow watches xena and wishes buffy would dress like her? Hmmmmm? Could will be gabby then? Note how she and Cordy end up 'in the closet' together at the end off school hard?
Did Nicky beg? In Damage we find out she did, at least in her mind. Maybe she did beg out loud but by the time spike told buffy the story in season 6 he decided to edit it to make himself look better?