Yes. The last time Hannah and Owen replay their scene, "Owen" says point blank that he's her.
Hannah's subconscious was having "Owen" say certain things in order to help her consciously realize that she's dead.
This journey through her mind and memories and other ghosts' memories was triggered by (the real) Owen asking Hannah to go to Paris with him. That's not possible for her, but she didn't know it because she hadn't accepted that she's dead. Up until that moment, she could carry on just fine not knowing this, because there's nothing about her existence at Bly that requires her knowledge of being dead. But then Owen asked her to go to Paris, and she loves him and would at least consider agreeing. So her subconscious knew it was time to make her aware that she's dead.
I think her subconscious picked Owen for two reasons: Again, she loves him. Second, he's a man who has thought and also experienced a lot about how minds and memories work; he told her about Thomas Merton's writings.
Poor Hannah. I suspected she was dead, on account of her not eating, but was hoping it was a red herring since she and Owen are so cute together. And while Hannah always seemed okay with the idea of Bly being her home forever, Owen clearly wants to leave the area. I don't think he'd be very happy if he died and had his ghost trapped at Bly, even with Hannah.
Rebecca insisted that there are times when Peter's "himself" and when he's not, and Peter didn't seem to remember speaking to Rebecca nastily the previous time she'd seen him. That's certainly very much like Miles's possession, now isn't it? I think Peter, like Miles, was inhabited by an older ghost who's the really nasty one, and when Peter died, that ghost switched to Miles. And Miles also has Peter's ghost hanging around...