What is the ruling on disassociating oneself from a sister who does not respond to advice and guidance regarding her immodesty (tabarruj) and her sitting with non-mahram men (ajaneb)? Is this disassociation permissible (halal) or forbidden (haram)?

It is not permissible for a sister to display her beauty in front of her paternal cousin or to be in seclusion with him, nor is it permissible for her to leave the house if her leaving would lead to corruption, because the fundamental principle for a woman is to remain in her home, as Allah Almighty says: "And abide in your houses." It is advised to be patient with her and continue to counsel her gently. It is permissible to boycott her if her benefit is hoped for through it, but if it is feared that boycotting her would increase her obstinacy, then abandoning it is preferable. Disavowing her bad actions is permissible, but defending her at a time of injustice is obligatory if the questioner is capable of it. If her guardian is present, then he is responsible for her, otherwise it is obligatory for the questioner to do so. It is advised to supplicate for her guidance.