Elena: ”You found a way to save the life of the doppelganger?”
Elijah: “Yes, Elena. I did. But unfortunately, Katerina took matters into her own hands first. I believe you already know how that played out.”
AU meme: When Katerina tried to kill herself, it wasn`t Rose who give her blood, it was Elijah. He wanted her safe and human, because of the elixir. As we all know, Katerina hung herself, not knowing the whole story.