I say, and with God's success: The ruling on hijab is obligatory for every mature, sane Muslim woman. If she neglects the hijab while the conditions are present, she is committing a great sin by exposing her private parts in front of non-mahrams. She is among those who openly disobey God Almighty and causes harm to Muslims. It is feared that God Almighty may seal her heart due to her insistence on sin, and she should hasten to repent to God Almighty. And God knows best.