But his initial reluctance to do rise to his little sister's defense amid her addiction reveal — borne from his desire to get his old post back — will change his relationship with her forever, says Caterina Scorsone.
"She finally is able to disengage from the childhood dynamic she's always had with him when he was the alpha and she was the beta," the 33-year-old actress tells The Hollywood Reporter. "She realizes she's pretty great. Her life was destroyed, and she built it back up from nothing on her own without his help. He's no longer this untouchable golden child. She realizes that she has as much strength and skill and integrity as he does. It really changes the way their relationship dynamic plays out. By the end of the episode, Derek approaches her and tries to make some sort of amends about it. But something has been broken there."
So the sibling rivalry may be over, but the sibling independence has just begun! We'll be eager to see more of Amelia 2.0 as Season 11 progresses.
Grey's Anatomy airs Thursdays at 8 p.m. ET on ABC.