Is there any religious evidence supporting the covering of a woman's grave with a piece of cloth as a curtain, given that she is required to observe hijab even after her death?

It is recommended to cover a woman's grave when she is being buried because it is more concealing for her. There is no disagreement among scholars regarding its recommendation. It has been narrated from 'Umar, 'Ali, Anas ibn Malik, and others that they used to cover a woman's grave, because a woman is 'awrah (private, to be concealed) and it is not safe from the possibility that something of her may appear and be seen by those present. The covering continues until the bricks are laid over her.