Biggest Piece of Evidence: Aria has a lot stacked against her. This week, we learn she wasn't at the hotel when Charlotte was killed. She swears up and down she had nothing to do with it, but we can't know for sure. Plus, she's the only liar who protests against Charlotte's release.
The Point of Contention: Aria is terrified of Charlotte. There's a slim chance she'd want to go seek direct confrontation. Plus, if we've learned anything, the most likely suspect is often the last person we should be looking at.