Okay so Sara probably is Sara but what if her twin was Bethany?
We know Bethany was in Radley, probably the time Charles was there. They must have met. Charles tells Bethany his story. They become friends. Bethany was younger so maybe he thought of her as his sister Ali.
Maybe Bethany told Sara she had escaped and wants to meet. Charles sends Ali the yellow top, Bethany sends Sara one too. Sara goes to Rosewood to find her twin. Only she sees one of the liars hit her.
Maybe it’s all Sara’s plan. She and Charles are working together to get revenge for himself and Bethany, Charles’s friend and Sara’s twin.
What do you guys think?