Operation Unidentified Corpse

In this part, the police officers find the body of a girl near the seashore. She does not have any papers or identity with her, and after matching her fingerprints, they were able to identify her. But the surprise was when Officer Amir went to tell her sister about the matter and found the girl there!! So who is the owner of the body and how did her fingerprints match the fingerprints of this girl...