Biggest Piece of Evidence: Of all the liars, Emily seems to be the most lost right now. It's clear she doesn't feel like she got her life back. Maybe she wants Charlotte to pay for taking away her chance at happiness.
The Point of Contention: Of the four girls, Emily seems the least affected by Charlotte's release. In fact, she's very focused on her dad's death, and her inability to function in school. Charlotte seems far out of her mind.