"I talked to my daughter at the end of last week. She is being held at the Kurdish camp for refugees, she is being interrogated and tortured," the woman told the Ouest-France newspaper on Tuesday.
She wants to ask French Foreign Minister Jean-Yves Le Drian to assist in the repatriation of Koenig, who "is asking her family, friends and country" for a pardon.
Koenig, 33, reportedly adopted radical Islamist ideology after being influenced by her first husband, who was of Algerian descent. In 2012, she left France for Syria leaving behind two children and recruited at least 200 French citizens to fight for Daesh. Koenig, who changed her name to Ummu Tawwab, has also called for attacks on French government facilities and servicemen.