If my co-wife dies, do I receive anything from her estate?

No. There is no inheritance between co-wives because they are not related to one another by lineage or marriage. The estate of a co-wife who dies is inherited by her husband, her children, her parents and other heirs under faraid. However, your children and hers are paternal half-siblings; if one of the children dies without closer heirs, paternal half-siblings may inherit. Co-wives may give each other gifts, or one may bequeath up to 1/3 of her estate to her co-wife, since she is not an heir. Keeping good relations between co-wives is strongly encouraged for the children's sake. See barriers to inheritance.