Hijab is an obligation upon Muslim women, not a label or distinguishing identity as some may understand or assume. So, you have to bear in mind that we are not allowed to take the Qur’anic verses out of their contexts, or to interpret the Qur’an without referring to authentic books of tafsir and acquiring specific qualifications that enable to drive rules from the basic sources of Shari`ah.

Given the above, it’s not passable to say that a woman who does not wear hijab is out of the fold of Islam.