Okay, so I think that Hester is the girl because her and Boone look similar enough. I don't think she died but her spine or whatever got fixed. I think so because Sam wouldn't know what Melanie looks like and probably would've questioned why Boone was still alive. Plus, she told the story about the car and the truck so it would make sense that Boone would know about it. Also, she's creepy enough to kill her brother as well as a bunch of other people.