English Translation
She asked me how old I was.
Doesn’t this mean, “You asked me how old I was”?
English Translation
She asked me how old I was.
Translation is incorrect. This means, “You asked me how old I was.”
The Japanese sentence could mean the subject is “you”, “she”, “they” or anyone else. “You” isn’t the only subject we often drop from a sentence. So, you cannot say the translation is “incorrect”.
Also, 私に言った should be replaced with 私に尋ねた (pron. たずねた) or 私に聞いてきた (pron. きいてきた) if it’s a pure question. あなたは何歳ですかと私に言った can be interpreted even as a complain - “Aren’t you supposed to behave like a decent adult? How old are you?” is the connotation behind 私に言った in this sentence structure.