If she felt uncomfortable with the question, declining to answer is fine. If I were in her shoes, I’m not sure if I would answer. I think it would depend on my sense of where he was coming from. I might ask why he wanted to know if I were suspicious.
And… I want to offer a different perspective here.
Why is talking about money so taboo in our culture? What’s so private about money? It seems old school to me to hide how much people make. If all the books were open, I think we would have a much more fair, equal society.
Sure, it’s a risk to actually own up to how much we make. Who knows what the person will think? What if we make less than them, more than them, if they’ll ask us for money, etc. A lot of fears can come up. My take is in general, the less hiding, the better.