My wife was very uncomfortable lending money to her brother-in-law without asking my advice. First of all, my own income is not high, and my wife's share is only enough to support myself.

Tell her what you have to say, don't keep it to yourself. Nowadays, many women take their husbands' money for themselves and spend it as they want. If she goes on like this, she can leave it in her hand. Women don't give money to men for fear that men won't do their jobs, so as long as you don't wander, my family is just like you, and I have a deep understanding.