Into every generation a Slayer is born. One girl in all the world…
To be a Slayer, or THE Slayer, means to be alone , to bring forth death and avert apocalypse and save the world over and over again with no thanks or praise because of the secrets and lies that come with the Calling. Buffy Summers is one such person.
Chosen to stand against the vampires, the demons, and the forces of darkness. She is the Slayer.
Through seven years of mistakes, growing up, maturing, accepting responsibility and making sacrifices, Buffy had survived. She only had to die twice, kill her boyfriend/lover, put her friends and family in danger, run away, kill a giant mayor-snake, avert an apocalypse or two and give up her power completely in order for the Potential Slayers of the world to become Slayers and help save the world. So Buffy is no stranger to sacrifice and responsibility.
In point of fact, in every episode of Season One, Buffy makes at least one sacrifice per episode. And not just the classic ritualistic sacrifice where animals are killed and demons are paid homage. Everyday life, where Buffy tries to lead a normal life, and have friends and boyfriends and do normal high school stuff, gradually she realizes she cannot do any of that. She lost friends and family for the sake of her Calling, and she made that choice over and over again.