The fast of a woman who does not wear the hijab
I don't wear the hijab. Will Allah accept my prayers and fast?
Hijab, the legal attire of a Muslim woman is a duty imposed by Allah the Almighty. He prohibited her from exposing those parts of her body which she has been commanded to conceal from men who are not of her unmarriageable kin. The legal attire is that which conceals the entire body except the face and hands; it must not be revealing, transparent or cling to the body.
All legal duties must be observed
The various legal duties are not interchangeable. For instance, it is impermissible for one who performs prayers to forsake fasting. Similarly, praying and fasting do not justify that a woman neglect wearing the legal attire.
A Muslim woman who prays and fasts but does not wear the legal attire which Allah commanded her to wear is blameless with regards to her fast and prayers but blameworthy for not wearing the hijab which is obligatory. Whether Allah will accept her fast and prayers is a matter that is left to Allah the Almighty; a Muslim is obliged to think the best of Allah the Glorious even if he or she has sinned or disobeyed Him.
Allah is most Merciful
A Muslim must know that one of the many kinds of mercies that Allah extends to man, is His decree that good deeds erase the bad and not vice-versa. A Muslim must also open a new page with Allah, repent from any sins and make the month of Ramadan the starting point for embarking on good deeds that would lead him to Allah the Almighty and earn His favor.
A Muslim woman, upon who Allah has bestowed the gift of prayers, fasting during Ramadan and obedience to Him must show gratitude by performing the duties she has neglected. This is because one of the signs that a good deed has been accepted is being conferred the success of following up that good deed with another.
Allah Almighty knows best.