She is not Darya Nikolayevna Saltykova. Daria Petrovna Saltykova’s Wikipedia article is here. It makes no reference to her children. Her genealogical sketch in gw.geneanet.org mentions only one her children. However, the Wikipedia article for her husband, Ivan Petrovish Saltykov, has this, "Together they had four children: Praskovya (1772—1859), Ekaterina (1776—1815), Anna (1777—1824), and Pyotr (1784—1813). The daughters all served as ladies-in-waiting at the Imperial Court, and two went on to marry and have children. Pyotr followed in his father's footsteps as a cavalry officer. He became a decorated colonel in the army during Napoleon's Invasion of Russia, but died less than a year later from medical complications that resulted from being wounded in battle."