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.
Health insurance, like other types of commercial insurance, is forbidden. It is an undefined contract so it is like gambling. It also involves eating people's money without right. Thus, it is not permissible for a Muslim to deliberately subscribe to this kind of insurance. However, if one is obliged to do so, it is permissible for him to benefit from this insurance but one should not exceed the amount that he has initially paid the company without any excess. So it is permissible for you to benefit from this insurance according to the previous condition.
Furthermore, we advise you to be patient and supplicate Allaah as much as possible, for instance you may supplicate with the supplication that the Prophet made: "Allaahumma akfinee bihalaalika 'an haraamika waghninee bifadhlika '
In addition to this, you have to take the appropriate means, like seeking the help of charity organizations or the help of good and righteous Muslims.
Finally, we ask Allaah to cure your wife from every disease.
Allaah knows best.