Is it permissible to marry one of my female cousins who have converted to Hinduism and now worship idols?

A Muslim man is not permitted to marry a polytheistic woman, based on the words of the Almighty: "And do not marry polytheistic women until they believe." Scholars have made an exception for a free, chaste woman from the People of the Book, based on the words of the Almighty: "and the chaste women from among those who were given the Scripture before you." Hindus are polytheists and are not People of the Book, so it is not permissible to marry a Hindu woman as long as she remains in her polytheism.