>>718047798
She got old.

Yes, drow get old. Its pretty rare because drow society runs on murder, but Yvonnel Baenre managed to reach old age in the books, largely by being the matron of the top house and a ridiculously powerful cleric. In addition, drow that somehow effectively defect from Lolth, escape Menzoberranzan and manage to make a life for themselves elsewhere presumably can reach old age.