It is Wajib (obligatory) on Muslim women to
wear the Shar`y veil covering their faces and hands in front of non-Mahrams (not spouses or unmarriageable relatives). You must continue advising your sisters in a gentle manner with wisdom and good counsel so that Allah may guide them to the truth. If they respond to you, all praise be to Allah Alone, but if they reject your advice, you must dissociate yourself from them. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.