We do not know any proof on the permissibility of differentiating between the grave of a woman and the grave of a man with a stone or suchlike and the basic ruling is that there is no need to distinguish between the two.
It is forbidden to
write on the grave whether the name of the buried person, (Part No. 9; Page No. 55) the date of his death or anything else because of what has been
that the Prophet (peace be upon him) prohibited writing on graves...
The Sanad (chain of narration) of this Hadith is Sahih (authentic).