I believe as all good Muslim women, we must wear hijab, it is stated in Holy Quran, but if hair is modest looking one does not need to be concerned about the purpose of hijab to maintain the modest appearance of a woman in spite of interested or not interested men who she may encounter in daily life, we all have sin and must pray that Allah forgives those sins. Although every effort should be made as a woman in islam to be covered from head to toe with hijab.