What if Spike met Buffy before she was called as the Slayer?

At a young age – somewhere between 10 and 14 – Buffy ends up getting lost in LA and is almost raped. Spike shows up and kills the man, and seeing the traumatized Buffy, can’t bring himself to feed off her. Buffy notices his vamp face, which leads to him telling her that he’s a vampire, but Buffy isn’t afraid because he just saved her.

On the way home, she and Spike end up bonding, which does something a little funny to the vampire’s heart. But he tries to forget about it and the girl he saved. He drops her off home, and Buffy doesn’t tell her parents about the attempted rape.

When Buffy is called as the Slayer, she’s told by Merrick that all demons are bad and all humans are good. But recalling the almost rape some years before, she realizes that this isn’t true; humans can be evil while demons can be good.

Buffy still carries out her duty – since the vampires she slays are obviously evil – but she doesn’t view the world as black and white. She tells this to Giles and ends up confessing what happened to her before. Maybe she tells Giles that she unintentionally gave Spike and invite but he never used it to his advantage, which makes Giles think.

When Jesse gets turned and killed, Buffy tells Xander that maybe there was a hidden dark side to his friend that none of them, not even Jesse, were aware of. This eases Xander’s demon hate.

In regards to Angel, Buffy is unsure what to make of him. She points out that a soul doesn’t automatically equal good, and is put off by Angel’s evil past. She allows him to help, but doesn’t let herself fall for him.

When Spike shows up, Buffy recognizes him immediately and is happy to see him. Spike is shocked that the girl he rescued years before has grown up to become the Slayer. When Buffy offers to help him cure Drusilla, Spike can’t bring himself to kill her and accepts the help. She discovers his past killing Slayers, and while she’s hurt, she gets over it because Spike continues to be nice to her.

Where it goes from there is up to the author.