What is the legitimate Islamic way to deal with sisters who are blackmailing their elder sister with a video and photos of a previous relationship, threatening her with scandal and ruining her life, and preventing her from studying, despite her repentance and regret, and how can she get out of this ordeal, and is her supplication against them permissible?

Whoever has transgressed against themselves with sins should know that the door of repentance is open, and that they should turn to their Lord and strive in His obedience, making their sole concern the pleasure of Allah Almighty, certain that Allah will ease their affairs if He knows the sincerity of their repentance. To strengthen faith, they should seek beneficial knowledge, read the Qur’an, consistently engage in remembrance (dhikr), perform many supererogatory acts of worship (nawafil), and associate with righteous people. As for those who mock her, she should ignore them, for Allah’s mercy is vast. Regarding the malice of her sisters, she should remind them of Allah and explain to them that she has repented and that injustice will be darkness on the Day of Resurrection. If they do not desist, she should seek Allah’s help and rely on Him, for Allah does not abandon those who turn to Him and are sincere in their repentance, as Allah Almighty says: "Indeed, Allah is with those who fear Him and those who are doers of good" and "But if you are patient and fear Allah, their plot will not harm you at all. Indeed, Allah is encompassing of what they do." And let her recall the saying of the Prophet, peace and blessings be upon him: "Be mindful of Allah, and Allah will protect you." Also, the incorrect phrase "were it not for the kindness of fate" must be corrected, for kindness (lutf) belongs to Allah alone.