WRONG, WRONG, WRONG! (CHINESE BREEZE - LEVEL 1) 2E ÉDITION

June 8. Beijing. A pretty girl lies dead on the floor of her luxury home. A slip of paper found on her body reads. "I'm tired. Let me leave... At the bottom of the slip is a signature : Lin Shuangshuang. Shuangshuang has a twin-sister called Duidui. The two girls look so similar that others can hardly tell who's who. Is the one who died really Shuangshuang ? Then where is Duidui ? If the one who died is Duidui as someone claimed. then why is the signature on the slip Lin Shuangshuang ?