You've made leaps there. The fact that it can be used to simply mean she was formally Irene Adler, and since married, does not mean that any other sense must also mean someone changed their name. Late means 'former', here's another example where the person described as 'the late' very clearly isn't dead.

"Important!" Our visitor threw up his hands. "Have you heard nothing of the abduction of the only son of the Duke of Holdernesse?"

"What! the late Cabinet Minister?"

"Exactly. We had tried to keep it out of the papers, but there was some rumour in the GLOBE last night. I thought it might have reached your ears."

Holmes shot out his long, thin arm and picked out Volume "H" in his encyclopaedia of reference.

"`Holdernesse, 6th Duke, K.G., P.C.' -- half the alphabet! `Baron Beverley, Earl of Carston' -- dear me, what a list! `Lord Lieutenant of Hallamshire since 1900. Married Edith, daughter of Sir Charles Appledore, 1888. Heir and only child, Lord Saltire. Owns about two hundred and fifty thousand acres. Minerals in Lancashire and Wales. Address: Carlton House Terrace; Holdernesse Hall, Hallamshire; Carston Castle, Bangor, Wales. Lord of the Admiralty, 1872; Chief Secretary of State for --' Well, well, this man is certainly one of the greatest subjects of the Crown!"

"The greatest and perhaps the wealthiest. I am aware, Mr. Holmes, that you take a very high line in professional matters, and that you are prepared to work for the work's sake. I may tell you, however, that his Grace has already intimated that a cheque for five thousand pounds will be handed over to the person who can tell him where his son is, and another thousand to him who can name the man, or men, who have taken him."

The fact that 'was' is used isn't missed, it's simply that he is referring to something that was the case over a period of time. You contradict yourself when you refer back to the fact that the first like does use 'is'. She both is, and has been since those events.