Imam al-Shafi'i (may Allah have mercy on him) said: "The view of many of the people of fatwa is that she (the divorced wife of a sick man) will inherit from him during the iddah; the view of some of our companions is that she will inherit from him even if the iddah has passed; some of them said: even if she has married another husband; others besides them said: she will inherit from him as long as she refrains from (marrying other) husbands; and in the view of some, the irrevocably divorced woman will not inherit. This is among the matters in which Allah Almighty's guidance (istikharah) has been sought."
Ibn Abi Mulaykah (may Allah have mercy on him) says that he asked Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) about a man who divorces his wife irrevocably (battah), then the man dies while the woman is in her iddah. Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) said: Sayyiduna Abdur-Rahman bin Awf (may Allah be pleased with him) divorced Tumadir bint al-Asbagh al-Kalbiyyah (may Allah be pleased with her) irrevocably, then he died while she was in her iddah, and Sayyiduna Uthman (may Allah be pleased with him) made her an heir. Sayyiduna Ibn al-Zubayr (may Allah be pleased with them both) said: In my view, an irrevocably divorced woman does not inherit.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الخلع والطلاق / 15124