Praise be to Allah.
She should start her ‘iddah from the time that he was found dead, because this is what is certain, and it (‘iddah) is four months and ten days, during which she also has to observe mourning, unless she is pregnant, in which case it ends when she gives birth, because Allaah says (interpretation of the meaning):
“And those of you who die and leave wives behind them, they (the wives) shall wait (as regards their marriage) for four months and ten days”
“And for those who are pregnant (whether they are divorced or their husbands are dead), their ‘Iddah (prescribed period) is until they lay down their burden”
And because it is proven that the Prophet (blessings and peace of Allaah be upon him) advised Subay’ah al-Aslamiyyah that her ‘iddah had ended when she gave birth. Saheeh, agreed upon.
And Allaah is the source of strength. End quote.