What should I do when the money in my possession decreases despite me counting it several times, and my wife denies taking it, even though I don't make her feel the shortage?

Money must be safeguarded by placing it in a secure location, out of reach of others, so as not to tempt anyone to steal it. This involves taking precautions and relying on Allah, as the Prophet, peace and blessings be upon him, said in Sahih Muslim: "Be keen on what benefits you and seek help from Allah." Those who wrongfully harm believing men and believing women have committed a grave sin.