What is Sister-7 doing ?

There are seven sister in a house in a village where there is no electricity or 

any gadget.

Sister-1: Reading Novel

Sister-2: Cooking

Sister-3: Playing Chess

Sister-4: Playing Sudoku

Sister-5: Washing clothes

Sister-6: Gardening


what is Sister-7 doing ? 

She must be..... 

Source 
 

Playing The Chess Alone?

First read the question. 

Sister -7 must be playing Chess with Sister-3.Remember there is no gadget in room.So sister -3 must not be playing Chess on a smartphone, tablet, laptop or desktop PC (no electricity). Every other activity can be done individually but for playing Chess you need partner at the other end.