Ok, I know we have been told way to many times that Libby's back story will not be told!
But after all I've read I still can't work out what she was doing in the metal hospital and why she gave Desmond the boat.
This may have been said before but my theory on this, is maybe she played a similar role to Matthew Abaddon and her job was also to get people to "where they needed to be". I know Abaddon was never on the island but he has a connection getting to people there, just as she is connected to Desmond by giving him the boat.
Be good if they did show this back story as a surpise, as whatever her past was/is, I'm sure it'll please alot of people to see it.