spouse hided serious illness before marriage

My brother got married to a girl inside raltive. But after a week of marriage my brother got suspicious on her moves and took her for a surprice doctor chekup and doctor strongly noticed it to be cancer and refer to manipal hospital. There she found having toungue(stage 4) cancer. This has been hidden from girls family till marriage. Later, the girl went on treatment in her native for moethan year. My parents called them for a meeting and asked them solve this hurdle and give the volunteer separation. But, they said she is being treated and will let you on the latest status next month, but they didnt turn back for morethan a month. Later, they started demading money for maitenance 5Lakhs. We said why should we give money, instead you should componsate for the loss you made to us. Later on many telephonic converstaions happened between the parents and the people involved in marriage arrangement. Finally yhey came to an agreement to mutually separate, as a matter of maintenance my parents agreed to pay money, as to save my brothers future from being ruined due to this prologning issue. Then we booked a lawyer to facilitate mutual divorse procedure. The laywer discussed with girls family and their lawyer and took their agreement. This month the date was fixed to visit the court to register for mutual divorse, both the faimilies brought the gold to return which they has exchanged during marriage. Both the families went for gold genuinity check and took notary sign also. But, girl denied to sign at the end saying i need my husband, her mom and brothers are not ready to take care. If my brother restricts, she will come to my brothers house and commit suicide. (in one-on-one discussion with brother, she said to my brother "any of us lodge a case your brothers marriage will be delayed") Meantime, in the prelitigation meeting other lawyers warned her that if you speak like this or if you try to go to his(my house) house we will handover to police. Our lawyer asked the lawyer designated by girl side, why did you changed the statement at the end. He said, it not my statement , all came from girls side. They asked for 15 days time. But the lawyer designated from our side said, no point in waiting for 15 days. It is been long time we have been discussed and came to this decission. Take a day or two and confirm, we are not going to force the girl to sign. We know the ways to get the divorse without her signature too. Now, lawyer from our side told whe will file a divorse petition by stating the girl never lived with the husband for morethan a year and need divorse. Lawyer said, that we will claim her cancer issue as it would add sympathy issues and would trouble the divorse request. Plese let me know the best solution for this. Anonymous