Once she reaches the threshold, she turns back yet again -- for a parting glance. Oh my word. Is she Katherine? Is that why her clothes have changed? What is she doing? She's sneaking down to the dungeon and pulling the dagger out of Elijah. She is Katherine! Wait, SHE IS NOT KATHERINE. Ahhhhh show. You're confusing me.
Let me think this through. Katherine is with Klaus, under his compulsion, stabbing herself in the leg. At the top of the hour, Klaus outright stated he does not want Elijah resurrected. There's no way Katherine has gotten free to pull the dagger out of Elijah, unless Klaus has willed it, right? And Klaus wouldn't will it, because he is glad Elijah is dead and would like him to remain so. All right. So that's just Elena sending Damon a, "Screw you Damon, you are not sacrificing Bonnie for me, and that's that," message, in a show-don't-tell way. Okay. Whew. That really messed with my head. Was it just me? Anyhow, Elena pulls the knife out of Elijah and then slumps to the floor and waits for him to resurrect, because she does it her way, damn it. And yes, it's going to complicate things, but I love that Elena is not passive about her life and the lives of her friends. Also, I love me some Elijah, so pull that dagger out, girl!