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.
You should not look at the answer without looking at the question. The question you are referring to states that a man has a sick mother and a sick wife, and he has only enough money to provide for the treatment of one of them; so the answer came according to the question. Indeed, we pointed in the answer that as a way of being kind to his wife, the husband should provide for her treatment if he is capable.
You should know that the view of the majority of the scholars among whom are the scholars of the four Schools of jurisprudence, is that the husband is not obliged to pay for the treatment of his wife. Nonetheless, some scholars are of the view that the husband is obliged to pay for the treatment of his wife, and some contemporary Fatwa authorities have chosen this view.
As regards whether or not the wife is obliged to serve her husband, then according to the preponderant view of the majority of the scholars she is obliged. This is because it is commonly known according to people’s customs that a woman serves her husband; this applies whether or not the husband is sick.
For more details, please refer to Fatwa 86344.