The big reveal at the end of the episode is that Claire's mysterious "friend" was Locke/Jacob's Nemesis. She said that she had talked to her father (Christian Shepherd) and her "friend" during her 3 years alone on the Island. How is it possible that she talked to Jacob's Nemesis, in the form of Locke, if the real Locke was either time-traveling or off the Island during the time frame that Claire was alone on the Island? I feel this scene makes us need to re-evaluate the connection between Locke and Jacob's Nemesis.
If what Claire says is true, then it leaves two possibilities in my mind. Somehow, Jacob's Nemesis was posing as Locke before the real Locke died. If the person in question is not dead, then Jacob's Nemesis might be able still "possess" their body. This could explain the visions of Walt that Shannon and Locke experienced in Seasons 2 and 4, respectively. Because Walt was certainly not dead. Perhaps Jacob's Nemesis needs the people he's possessing to be dead to physically interact with other people, such as beating the hell out of Richard. The other possibility is that the appearances of Locke to Claire during her time alone on the Island was the work of Jacob, which is an interesting thought. It's been theorized that for Jacob's Nemesis to take someone's form, the original person needs to be dead. Maybe these rules don't apply to Jacob and he can appear as anybody. It would be an interesting idea that Claire was influenced by both Jacob's Nemesis (as Christian Shepherd) and Jacob (as Locke) during that period of her life. Now it'll be total confusion for her as Locke will now be appearing to her, when it'll be Jacob's Nemesis. If neither of these are true, then I have no idea what to make of that final reveal. Which happens a lot with Lost. What do you guys think of Claire's "friend?"