The phrase ‘That’s all she wrote’ is an idiomatic expression used to indicate that something has come to an end or that there’s nothing more to be said on a topic. Its origin can be traced back to the idea of a letter or message concluding, suggesting that the writer has finished their thoughts and there’s nothing left to add.
In conversations, when someone uses this phrase, they usually emphasize that the situation is final or that there are no further details to discuss. It might be used in a variety of contexts, from summarizing a story to expressing resignation about a situation, effectively indicating that the speaker feels there is no more to be done or understood.