Q. I know for women and girls who have reached the age of puberty (baligh), it is compulsory for them to cover the entire body, except the face and hands up to the wrists. What about a woman, who is 16 or older and has never experienced such haidh? What would be the exact ruling for them?
A. If a young girl is growing old and she has not experienced her menses, then the age of 15 years will be considered her age of puberty. This means that all the laws of Islam like Salaah, fasting, etc, will be effective from this age. She will also be accountable from this age, and she will be required to start wearing hijab. (Raddul Muhtaar vol. 6 pg.154).
The Fuqaha (jurists) have also stated that if a young girl has such a built or physique which can be a means of attraction to the opposite sex, then she will be required to wear hijab and cover herself properly even though she may have not reached the age of puberty (through menses) or the age of 15 years.
And Allah knows best.
Mufti Waseem Khan