All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is no doubt that it is a great sin to consume forbidden money. This could lead to many bad consequences in this life and the Hereafter. For instance the supplication of a person who earns from forbidden sources is not answered and he could be punished in Hell-fire. The Prophet said: "The flesh that is fed on forbidden money then fire is more appropriate to consume it." [At-Tirmithi]
Therefore, this wife has to endeavour to guide her husband to righteousness, with soft and good words. She has first to seek the help of Allaah, then the help of whomever she thinks can influence him, especially the scholars who might be a reason for his repentance. If she has no money to live on without depending on his money, then the ruling of a person who is in necessity applies to her. So it is permissible for her to eat from his money according to the necessity-if she eats enough to stay alive, she should refrain from eating more. In this case there is no harm on her. Of course, eating according to the necessity applies if all his money is gained from forbidden sources. However, if his earnings are mixed between forbidden and legitimate earnings, then it is just dislikeable to eat from his money. It should be noted that the Sunnah was reported about the supplication of a person who earned his money from forbidden sources, that it will not be accepted from him, but we do not know any evidence that other acts of worship will be rejected.
Allaah knows best.