Here it appears that the man's wife is not so free with him and maybe that's why his wife doesn't dare to say these words directly to her own husband. But I won't say what his wife wants is illogical or bad because on the one hand she is right because if her husband's habits gradually turn into addiction then later today there is a possibility of losing money which is bad for them. Circumstances may lead to this.
I think if a husband indulges in many vices starting from gambling, a good wife is enough to bring him back from them. Because a man can easily be destroyed by a woman if she wants to and can turn him from bad to good. So I think if one has a good wife then that person can never indulge in bad deeds because his wife will always try to keep him away from bad deeds.
Does that include praying for their failure?
Like I mentioned before, there are several ways to achieve this and choosing for someone to fail so that they’ll look your way shouldn’t be an option for you [unless you want to somehow repay them what they have lost and were supposed to win] - she could have spoken with those friends and let them know that the drinking was becoming excessive and they should help her talk to her husband if he could reduce it, that’s one option.
Another is to confront her husband, and tell him face on that she does not like the behavior and let him see the reason why - if he’s a good husband he’ll try his best to reduce it or perhaps even stop it completely for the sake of his wife. Those are far better options than praying her husband does not win so that he won’t see money to buy his drinks if he fails to win after several tries he’ll only turn to his pension money and start using from there to buy those drinks.