Considering Buffy's age when she said it, the fact that Angel was almost certainly her first serious love, and the inner conflict that she almost certainly had with the fact that Angel was a member of the very species that she was born to destroy, soul or no soul, added to the fact that her friends would almost certainly disapprove of such a relationship, I think that it's a pretty accurate, if overly dramatic, statement from her feelings at that particular moment. (Or maybe it was just a comment about Angel's blood breath) As happy as being with him made her feel, there was still that slight sense of shame and almost betrayal to the "Code Of The Slayer" as she saw it at that time.