Question: Should an eleven-year-old girl, who began to experience menstruation, fast although she does not enjoy good health? What should she do if she cannot fast?
Answer: If the case is as you mentioned, she has to fast because menstruation is one of the signs of puberty for women beginning from the age of nine. If she is able to fast then she must do it during the proper time. If she is unable to fast or undergoes extreme hardship in doing so, then she may break her fast but she must make up for the days that she missed when she is able to… read more here.