When does Elena become a vampire?

The Vampire Diaries, Elena discovers Stefan is a vampire in the 4th episode. Where at the end of the 4th episode, she writes in her journal and discovers herself. There she is seen going to Stefan, then Stefan opens up the door and the episode ends. At the beginning of the 5th episode, it is replayed, but when Stefan opens the door it goes into a flashback to 1864. Then he comes back to modern time and Stefan tells it to her.