Diplomatic Immunity shouldn't be revoked. It should be for the US Justice system to decide if she should be 'advised' to return to the UK. This way DI will be protected. As unsavoury as that might sound, the sanctity of DI has to be protected, and the responsibility should lie with the diplomat's home country to decide if the case is valid. Appreciate that might seem a bit skewed but there is a greater precedent to be protected.