My Sister, My Prisoner

A five-year-old girl went missing, and her father afterwards adopted an orphan who looked like her. Years later the daughter was found and returned, and the father named her successor at the company, with the adopted daughter to assist her. The adopted daughter agreed to this and then arranged a car accident. The father lost his memory and disappeared. She took his place at the head of the company and had Jenny committed to an asylum, where the staff and everyone outside were told Jenny was insane. She then lived as the heiress. Jenny gets out. The father did not die, and he finds her.