What is the ruling of Islamic law regarding a wife whose husband passed away and left her money which she deposited in Bank Misr for Islamic Transactions? What if this bank gives her fixed or non-fixed interest?

The financial transactions of the mentioned bank cannot be judged without knowing their true nature. For dealing with the Islamic branches of interest-based banks to be permissible, they must fulfill Sharia (definition) requirements. The money left by the husband is an inheritance that is divided among the heirs if its earnings were lawful. However, if it was interest-based, then it is unlawful money that should be spent on charitable causes and public welfare.