I have been faced with this problem from the day I got married my mother in law always quotes this instance and makes me speechless she tells that a man once came to prophet muhammed p.b.u.h and complained about his miserable financial status prophet mohammed asked him to marry another woman bit nothing improved then prophet p.b.u.h asked him to marry again and then his luck improved and he started flourishing,is there any such incident quoted in islam if so then what doesit actually mean?am I responsible for his misfortune

Why should you have to prove that she is right or wrong? People make up all sorts of quotes from holy books. Tell her you want to go to an imam to discuss this. Maybe the prophet had something to say about mothers and sons.
Women have been blamed for just about everything throughout history.