palabravampiress
Bidet of Evil
Like a lot of others have already said, I think the depravity of it had less to do with the sex itself than with the dysfunction of the relationship. What she let Spike do to her was get inside and draw out the darkness of which she was ashamed. She let Buffy go and indulged in the Slayer. Her season 6 fling with Spike was WRONG. It went against everything for which she'd ever stood -- and she *liked* it. Not only did she like it, but it was the only thing that she liked. It was the only thing that made her feel alive and real. No wonder that made her feel ashamed. What she let Spike do to her had less to do with the sex acts themselves than with the meaning of those sex acts: she let him hold a mirror up to herself and she didn't want to like what she saw.