Is the Hadith that states that a woman who performs ghusl after her menstruation and prays two rak'ahs, reciting Al-Fatihah and Al-Ikhlas three times in each rak'ah, will be forgiven her sins and receive the reward of sixty martyrs, authentic?

This hadith (definition) has no basis and is not found in the well-known books of hadith. It was only mentioned by Sheikh Abd al-Rahman al-Safuri in his book "Nuzhat al-Majalis wa Muntakhab al-Nafais." The fact that this book alone mentions the hadith is sufficient indication of its falsehood and fabrication, as it is a book filled with invalid reports. Sheikh Muhammad Rashid Rida warned against relying on hadiths that fill books of admonition, softeners of hearts, and Sufism without clarifying their source and degree, specifically mentioning the book "Nuzhat al-Majalis," which he described as being full of lies.