Hijab is a duty that Allah Almighty prescribes for the Muslim woman, and she has to carry out that duty in compliance with the Command of Allah, thus showing her sincere faith in Allah and fear of His punishment. For He says (And it becometh not a believing man or a believing woman, when Allah and His messenger have decided an affair (for them), that they should (after that) claim any say in their affair.) (Al-Ahzaab 33: 36)
Sheikh Ahmad Kutty, a Senior Lecturer and Islamic Scholar at the Islamic Institute of Toronto, Ontario, Canada, states the following: If a woman started wearing hijab in Ramadan, we should commend her for doing so. We are not supposed to discourage her by saying, ‘You are only doing so in Ramadan.’ A good deed is a good deed. It is also important for us as Muslims to use wisdom in da`wah; this means we should not act as judges, we should be looking at people with mercy.
the Prophet (peace and blessings be upon him) is reported to have said: “Make it easy and don’t make it hard on people, and give glad tidings and don’t turn people away.”
By wearing hijab in Ramadan, by doing so in sha’ Allah she may be encouraged to develop the habit of wearing hijab. Psychologists say that it takes a minimum of 21 days to break a bad habit and to start a new one. So, we should commend our sister for wearing hijab rather than discourage her.