S03 E09 – The Wish
Cordelia blames Buffy for unhappyness and wishes that she didn’t has come to Sunnydale. Without knowing, she wishes it in front of a demon who grants wish: Anyanka.
Immediately, she’s in a new reality where the Master is alive and runs Sunnydale. Xander and Willow are vampires, Giles tries to contain the vampires with Oz and some others students. Cordelia regrets her wish and come to Giles and try to explain him that Buffy had to be here and the life will be better. But she is killed by Xander and Willow.