What is the optimal course of action for this girl who has repented and regrets a past relationship, and is currently afraid that the young man she was involved with will expose her and threaten her with audio recordings containing private conversations? And is it permissible for her to deny this relationship and take an oath if her father comes to know of it, in order to avoid scandal?

Love relationships between young men and women are forbidden. Whoever has fallen into such a relationship must repent to Allah by abandoning it, feeling remorse, and resolving not to return to it. They must conceal their sin and not publicize it. If her father asks her, she should not tell him, as the Messenger of Allah, peace and blessings be upon him, said: "...O people, it is time for you to cease violating the bounds of Allah. Whoever commits any of these abominations, let him conceal himself with the concealment of Allah, for whoever reveals his shameful act to us, we will apply the Book of Allah to him." Repentance erases what came before it. Whoever fears Allah and relies upon Him, Allah will suffice him. Allah Almighty says: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect. And whoever relies upon Allah - then He is sufficient for him."