Biggest Piece of Evidence: Of all the four liars, Hanna seems, at first, like the most angry. Plus, as we see the morning after the girls' late night of drinking, Hanna is the first one to be awake. Could she have slipped out in the early morning?
The Point of Contention: The fact that Hanna, in the end, lies for Ali suggests that she's not hanging on to a lot of her anger when it comes to Charlotte.