What is the ruling of Islamic law on a wife who concealed her chronic illness from her husband, and her illness caused a miscarriage, and she refuses to waive some of her rights upon amicable separation?

The majority of jurists hold that the defects warranting annulment are those that prevent sexual intercourse or are repulsive and contagious diseases. The right to annulment is forfeited by consenting to the defects. If the wife's illness does not necessitate annulment, or if she consents to it, then it is not permissible for the husband to oppress her to redeem herself. If he does so, the khul' (divorce by mutual agreement, initiated by the wife, with compensation to the husband) is invalid, and the compensation is unlawful.