Is it permissible to ask a sister to divorce? And what is the obligatory action to take regarding the severing of kinship ties with the sister, her husband, and his family, especially given that the husband concealed his sexual disability and the inaccuracy of his educational qualifications, and that the sister is living a miserable life and receiving psychological treatment?

It is not permissible to incite a wife against her husband as long as she is content with him. However, if she desires a divorce due to his infertility or deceit, there is no blame. As for the harshness and estrangement of the family, it is not permissible. The sister must maintain ties with her parents, no matter how badly they behave. Advise her to abandon disobedience to parents and cutting off family ties, and you yourselves should maintain contact with her. If you suspect she is enchanted, treat her with legitimate ruqyah (definition) from trustworthy individuals; accusing someone of magic without proof is forbidden. Our advice to you is to try to reconcile and reunite the family by maintaining communication and overlooking minor faults, and to avoid delving into matters between her and her husband as long as she is content.