I would say "She was I", but Kooyeen delights in pointing out that I'm in a 1% minority. It comes down to, what do you mean by "correct"? - and what do you mean by "allowed"? - and what "register" would you like to represent?
I like to think of the song lyric from the musical, The Man From La Mancha: "I am I, Don Quixote!" "Correct grammar should be confined to art, and has no place in conversation."
They say the king of Spain once spoke with a lisp, so the whole country was required to follow suit. Perhaps some day the whole world will say, "nucular."