Sister being harassed

Hi All, Need some help regarding my elder sister. She has been undergoing some strange happening at her home currently. To give you some background, my sister got married approx 7 years back and shifted to her in laws place post marriage. Things were fine for some time but after that her in laws started creating lot of issues. On numerous occasions after instigation of her MIL my sister's husband hit my sister. Things got worse and my sister somehow got her husband convinced(after a lot fights) to move out. They now live separately but now my sister has been complaining of some strange things. Apparently her mother in law has been doing black magic on her and her son. My sister has been under tremendous stress and has sighted some unnatural things in the house. She fears for her life and she also has a 6 yr old son. We come from a progressive family and for my sister to believe in such things I am very sure that there have been such happenings in her house. I would also like to say that my sister has contacted a few tantriks to help her with this. She has been suggested to not take divorce by them as these things will continue even post that. We generally don't tend to believe in these things till they actually happen to us. Few questions: 1. As MIL does not stay with her, what can we do in such a case? As there is probably no solid proof. Her husband does not know anything about this and probably will not take her side. 2. As this is India, I am quote sure there are a lot of such cases. What would be the best way to approach this? The situation is extremely grave, appreciate any help.