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.
It is incumbent upon the husband to live and treat his wife honorably as Allaah says (Interpretation of the meaning): {And live with them honorably}[4:19]. Allaah further says (Interpretation of the meaning): {And divorced women have rights (over their husbands as regards living expenses, etc.) similar (to those of their husbands) over them (as regards obedience and respect, etc.) to what is reasonable}[ 2:228].
So he has to sustain her and provide her with housing as well as satisfying her sexual needs. So we advise you, first of all, to take the initiative to reconcile between them, as it is good to reconcile, may Allaah bring him back to righteousness. If this is achieved, praise be to Allaah, but if he persists on staying on his position, then she can take the matter to an Islaamic court of justice, if any, otherwise to the Muslim community, i.e. she takes her case to an Islaamic Center or an Islaamic Foundation so that they would look into her matter.
It is also permissible for her to appoint you to act on her behalf in this matter.
Allaah knows best.