I remember reading a fic very much like
vampyrs99 is asking for. I thought I remembered the actual name but after skimming...nope.
It isn't new either. Back in the years story
.
As I recall Giles and Joyce aren't technically dating they are rather 'hot' for each other. They skirt around the issue until yes they end up kissing in the kitchen.
Joyce actually sees Spike and Buffy kiss while the others are in the kitchen. She sees the chemistry though Buffy hides it. The kiss was actually a request from Spike and I believe it was to convince Angel/us that they were dating? I'm not too sure if it was season 2 but it was definitely an earlier season. I don't think Buffy was turned. I do however believe she might have been tortured? I thought it was Demon In Me at first...but as I'm skimming the parts I remembered aren't there.
But I do have to agree with
Coednakedslaying that there are quite a bit of stories like this. Because if I recall in this story Giles was on Joyce's bad side for doubting her daughter. That's probably why readers haven't jumped in saying ooh oooh I know this!
I know exactly which fic you are looking for but I'm wracking my brain and coming up with a big...nothing.