“That’s all she wrote”, means that it is the end of something. It has a rather a heartbreaking story to it. The origins are from the Second World War, which spawned many other great things. In this case, Serviceman over the seas would receive letters from their spouses or girlfriends that they had found someone else in their absence. When the soldier would be asked by his companions about the break up, the soldier would say that’s all she wrote. So basically it picked on from there and on, it entered the standard language and our society, so whenever someone says it’s all she wrote it means something is over.
The term is not used much in daily conversations but when reading a piece of news, documents they often use this expression. It is also often used in sports by commentators, specially in combative sports, whenever the fight is over they often finish the broadcast with “and that’s all she wrote”.