Buffy wasn’t willing to listen to Giles today.
He knows she was the chosen one, one girl in all the world to fight the forces of darkness. But the Slayer’s role was of that of the hunter, and unfortunately of the hunted.
Giles knows she’s smart, she’s resourceful, her friends will keep her alive. But she’s also bull-headed and prone to running head first into danger. Her friends could help protect her in some situations, but when it was her own foolish pride that she was fighting. They couldn’t do much.
He just has to wait, pick up the pieces.