All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, we ask Allaah, The Almighty, to enable us and you to do good and to guide us and you and to rectify your sister and bless her with a pious husband who would keep her chaste.
The first things that we advise you to do is to look for a husband who is religious and has a good moral conduct to marry her and we have already explained the benefits of an early marriage for girls in Fatwa 116746.
Also, there are a number of steps to be followed among which are the following:
1- You should choose for her a pious company of girls who would guide her and whom she would take as an example.
2- You should supplicate Allaah to guide her and enable her to do good deeds, especially the supplication of her parents, as it is responded to.
3- You should not always allow her to be alone using the communication equipments in seclusion; so she should not be allowed to use them except in the presence of her family members.
4- You should use the different means of Da’wah with her, like audio and video tapes, useful and short brochures, and you should speak to her in a soft and gentle manner, as one may achieve with softness what he may not achieve with violence and roughness. Indeed, being too strict with her may lead her to do what is even worse than what she was prevented from doing.
Allaah Knows best.