To add to the discussion of Buffy cheating death, I agree that it probably did not happen much with slayers, because, as you said, most of them lived solitary lives, and Buffy's friends were instrumental in helping keep her alive. I also think that maybe Buffy's first resurrection didn't trigger the events that her second resurrection did was because Xander used "natural" means to revive her, while Willow used magic. Also, if you have more info on Slaypires, I'd be interested. I don't know if Buffy being one in Nightmares counts, since that was a nightmare, and I've always wondered what would happen if a slayer became a vamp. Would she be different than a regular vamp?
The thing that's "unnatural" is that there were two Slayers active at one time -- so it depends on if we're talking about how she was resurrected or the result of the resurrection.
I do think, not to veer totally off topic, it would have been interesting if the Slayer line had branched and we'd gotten a third Slayer called after Buffy's second death, instead of the idea that both Buffy and Faith would need to die to get a new one (per Buffy's random theory she suggested in Season 7 based on nothing since Faith was called when Kendra died.....smh....)
Slaypires started in non-canon comic books/novels, I think, but they were a big part of the post-TV show comic books. The Buffy wiki has a page on them, but the gist is that they were significantly stronger than vampires or Slayers because they have the combined powers (but also all the same weaknesses of regular vampires.)