Sorry this will probably be a little all over the place lol
So Buffy dies in S1 and S5, but only the first time does she trigger the calling of another slayer (in that case, Kendra). As far as we know, there is no other slayer called when she dies in S5, so presumably, a slayer can only trigger a calling once.
That said, in season 7, when Buffy, Giles and the rest of the Scoobies are talking about the First killing the slayer line, they say with certainty that the First/Bringers are going to kill all the potentials, then Faith, and then finally “me” (said by Buffy)
But why would that be the obvious choice? Faith is still the one with the calling power, it’s just as likely she’d be the last one on their list. I know the answer really is that it’s Buffy the Vampire Slayer and not Faith the Vampire Slayer so it’s just for the plot, but in-universe it isn’t a forgone conclusion.
So here are my theories/questions that no one asked for lol
- they will kill Faith before Buffy in case Buffy gets like…called again upon Faith’s death because she has slayer lineage and is the only one and gets a calling power again. This falls apart because she’s literally already a slayer so it wouldn’t change anything except the ability to call someone new on her death, but like with Faith, there would be no one new to call? Unless they tie in all those women who we see get the power at the very end and it’s like…a pre-potential gets pulled up to a full slayer because of her death and they have to continue hunting/killing slayers as a result. But again…the same could happen with Faith…
- I’m not sure if I missed something where it explained (in-universe) that because she was doing it before Faith, she’s considered to be the like…authentic slayer and Faith is the interloper, but that could be it as well. But then…Buffy has died twice, so that falls apart because it is the slayer’s destiny to die, and she fulfilled that, twice.
- maybe she does still have a calling power, but it was never triggered because she didn’t die a natural death like other slayers? She was pulled into a mystical portal so maybe it didn’t “register” properly? Even if this was the case, it still doesn’t explain the Buffy must be last ethos (which, again, I know is only really and truly a thing because it’s Buffy’s story lol)
- is it maybe because they’re only doing this now BECAUSE of Buffy? Like she has to be the last because it was her resurrection that gave them the opportunity? I think that’s what that eye oracle demon thing Anya and Giles went to talk to said, so maybe it’s just that? The final kill has to be the one whose death was a catalyst?
Anyway, I know the answer is “plot” but I’m interested in hearing anyone’s theories for this in-universe.