This is a season 7 one shot fic that starts with the Spike/Faith scene in the basement. Buffy is uber jealous and when she and Spike go on patrol that evening, she (I think) makes the comment about Faith trying to steal all of her boyfriends. i know it ends up with Spike and Buffy making love on patrol and I think love is professed.

Could it be Faith by smg fan? Its here on TSR

morkovka
No-that is not it. The one I am talking about is a little older and there is no confrontation with Faith (at least not that I remember.) it is only with Spike and happens in the grave yard. I am pretty sure that Buffy slips and says the boyfriend thing, Spike jumps on that and then Buffy jumps on him.

Tara
Did you ever find the fic you were looking for?

3/21/2012 update: Still an open case.