One in Nineteen

Elena finds photos of a girl Stefan says was his friend/fiance, Hattie Whitworth, from 1864. When Jenna's friend, Ally, returns, Elena and Stefan begin to wonder if Hattie and Ally are the same person. But how can Ally be Hattie if she still has a heartbeat? Why is she so close with Sheila Bennett? And why has Damon decided to follow her every move? Slightly AU; begins season 1x17