Why She's Guilty: Sara Harvey was Red Coat and The Black Widow. She was involved with everything the whole time. Plus, Emily and her friends are responsible for her new, damaged, fragile state. Her sudden reappearance in Rosewood is telling. Of course Sara would want revenge. Wouldn't you?
Why She's Innocent: As the police said, Sara is far too feeble to do any damage on her own. They even eliminated her as a murder suspect. So, unless Sara has help, it's pretty hard for her to wreak much havoc.