There is one chosen, who is in a continual replace line. First the Movie and then TV
When Buffy drowned, Kendra and Mr Pointy appeared.
Then, there was Faith, good then bad, with Angel and Back again
Switching Bodies with Buffy
so when Buffy was dead for the months before Willow brought her back
there was not a new slayer as there should have been
Justine Cooper would not have been Wesley’s prisoner if she’d been a Slayer
then, Buffy had Willow activate all the Slayers, depleting the magical line