What is the ruling regarding a Muslim woman who civilly married a non-Muslim, especially given that she has an inheritance from her deceased father and grandfather, and considering that she was previously married to a Muslim and has a child with him?

It is not permissible for a Muslim woman to marry a non-Muslim, whether he be Christian, Jewish, or otherwise, based on the Almighty's saying: "And do not marry polytheists until they believe," and His saying: "And never will Allah grant to the disbelievers a way [to triumph] over the believers." This prohibition is agreed upon by the Ummah. The relationship of a Muslim woman with a non-Muslim man is considered adultery (zina), which is a major sin, but it does not expel her from Islam. Therefore, she inherits from her Muslim father, grandfather, and husband like any other heir.