All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is nothing wrong for the wife to ask about the amount of money that her husband owns. This is a normal matter for women, so it should not be a source of worry for the husband; however, he is not obliged to tell her if she asks him about that, especially if he sees that the interest is in not telling her.
Her right upon him is that he should spend on her according to reasonable terms and according to his well-being, based on what Allah has blessed him with without extravagance.
Allah Says (what means): {Let a man of wealth spend from his wealth, and he whose provision is restricted - let him spend from what Allah has given him. Allah does not charge a soul except [according to] what He has given it. Allah will bring about, after hardship, ease.} [Quran 65:7]
The husband should be courteous with his wife if she asks him this question and the like, while he does not want to inform her of how much he owns, in order to prevent discord between them. In general, marital life cannot be stable except with some courtesy. Al-Bukhari said in his Saheeh:
“Chapter: To be polite and kind to the women.”
Al-Manawi said: “Politeness means gentleness, kindness, leniency, and courtesy.”
The husband should be wise and astute in dealing with this matter.
Allah Knows best.