My sister hates her family without any reason and I think that she is bewitched. I think that her husband has bewitched her because he often goes to magicians. What should I do?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

If you are almost sure that your sister is bewitched, then you should confront her and try to convince her that what she is doing indicates that she is under the effect of a magic spell. Also, try to convince her to seek treatment through Sharee‘ah-approved methods, which have been mentioned in other Fataawa on this site.

However, you have to know that it is impermissible for you to accuse a specific person of bewitching your sister unless you have definite proof. In fact, going frequently to magicians does not necessarily mean that your brother-in-law is the one who has worked magic on your sister. It is your duty, once you know that he goes to magicians, to advise him gently not to do so again. 

And Allaah Knows best.