Ahlul Sunnat say that according Shia belief, the parents of the Prophet and the Imams (a.s.) must be Muslim, so what can be said of the mother of Imam Zainul Aabideen (a.s.)?

The reply to this is according to a report of Allamah Majlisi in Jilaul Uyoon, is that Lady Fatima Zahra (s.a.) had taught Islam to Shaharbano in a dream. This made her long for the Prophet’s family.

She was also told the name of Imam Husayn (a.s.) and was given the good news that she was to marry him. Her marriage (Nikah) was performed to Imam Husayn (a.s.) according to perfect Islamic rites and she had become a Muslim before her marriage. Those who call her infidel are themselves the worst of infidels. She was a believer and remained a believer till the end of her life.