Did my preventing my sister from using computer headphones for a sinful purpose, and my father's allowing her to use the television for the same sinful purpose, lead to a greater sin, and what should I do, and should I give her the headphones?

The headphones are subject to two scenarios:

1. They are exclusively owned by the questioner: He must prevent his sister from using them for forbidden acts, while advising her gently, speaking kindly to her, and gifting her permissible things. If the headphones are jointly owned through shared use, he must prevent her from using them during his designated time. 2. They are owned by the sister or the father, and they have permitted her to use them: If preventing the sister would cause her alienation and persistence in wrongdoing or lead her to commit a greater wrong, then it is sufficient for the questioner to advise her with good counsel without preventing her. This is not considered cooperation in sin as long as the headphones are not his property, and there is no blame on him unless the greater wrongdoing is intended or highly probable in his estimation.