How should we deal with a female relative of ours who was caught red-handed performing acts of sorcery, such as placing donkey dung in front of our house, and claims it is a cure, knowing that her son is married to our sister, and are we sinful if we warn against her and monitor her?

Sorcery is one of the gravest sins, indeed, one of the destructive ones, as the Prophet, peace and blessings be upon him, said: "Avoid the seven destructive sins: associating partners with Allah, sorcery..." And going to sorcerers is forbidden, for he, peace and blessings be upon him, said: "Whoever goes to a soothsayer or a diviner and believes what he says has disbelieved in what was revealed to Muhammad, peace and blessings be upon him." It is obligatory to advise anyone who does this to repent and to warn them of Allah's punishment. If they do not desist, there is no sin upon you in warning against them and monitoring them.