Here is a fic where Buffy 'has sex' with Angel: All Ways. And how. I believe every second of it. (B/A, B/S, S/A, S/B/A. Everyone should read it. Mmmmm.)

I do not believe Buffy would have sex with Twangel, unless otherwise influenced.

Actually - remember Fred/Gunn and what broke them up? Don't tell me that something like that can bring people *together*.