Selling of property through certified copy of power of attorney

Sir my father was in defense services and could not deal with the suits that's why he gave POA to my paternal aunt to deal with all those suits. And afterward my father took back the original POA on oral instruction to not to deal with suits now.POA was not cancelled through the process of law but taken back on oral instructions that she nothing has to do with those suits now But she obtained the certified copy of the same and executed the sale deed without on the instance and instruction of my father and even without knowledge. Now my questions is whether she can execute the sale deed with the help of a certified copy of POA and if yes then whether the sale is legal.