Is the girl in the hospital Durga's sister?

I am really confused... She never said anything like that... She never said I will take revenge for my sis or something...If the girl in the hospital was her sister she must have the same name last name as Durga... Then how com Shrya( main lead) was not shocked after hearing Durgas full name... Even the raped girl dad was a well known man ... Then wouldn't he recognize him... Sure