Possible Ending 2:
Rogue slayers were something they mentioned in history books. Not in the present day.
So despite Giles' occasional comments, no one took it too seriously that Faith and Buffy would play a little loose with the rules, would take what they needed instead of working at a fastfood place to pay for it, would threaten or blackmail an official to keep custody of Dawn instead of forcing her to go to school.
Eventually, Giles went back to England, saying they could protect the town, between the two of them and Willow. But of course, Faith and Buffy sometimes had friction, and Faith eventually took off - amicably- to look for people who needed help other places. She hooked up with one of Angel's friends, Gunn, for awhile, before heading to hang out in Europe.
Buffy stayed in Sunnydale, fighting the good fight. In some other world, she would have been more careful, would have remembered that there was a line between being a leader and a thug, would have kept some bad example in mind as the kind of slayer she never wanted to be. But the injustice of being forced into a slayer life weighed on her, and as long as she killed vamps, it didn't seem like it was that important to follow the rules that ordinary humans did.
So when the Watchers' Council tried to test her, she didn't respond well. When they wanted to hold their knowledge of Glory over a barrel, she didn't let them. Hard.
When it came time to kill Ben, she did what she had to do.
When she was ripped back to earth by Willow's spell, she didn't try so hard to keep up appearances.
She also didn't hesitate to kill Spike when it turned out he could attack her.
When she beat the geek three into confessing on tape before they could get someone killed, Willow and Tara left. Dawn asked to go with them, and Buffy couldn't think of a reason to say no.
Xander left too, after she killed Anya. Snuck up on her, since she had demon powers.
For a while, she is alone.
Eventually, Giles comes back. There's trouble coming, he says, the Council has been destroyed. Young girls are being killed.
Buffy tells him that it's not necessarily a bad thing. At least this way, they'll know that the next Slayer will be someone who fought to get there, who had to survive attacks. Not just some girl who had power thrown on her until she wasn't her any more.
Soon, she sends Giles back to England. Buffy doesn't need the help.
