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.
We advise you to find out the reason for this animosity and to try to eliminate it using kind treatment and flattery. Allaah the Almighty Says (what means): {Repel [evil] by that [deed] which is better; and thereupon the one whom between you and him is enmity [will become] as though he was a devoted friend.}[Quran 41:34]
Kind treatment often turns enmity into affection. The questioner should also ask his wife to do the same.
If the grandmother insists on continuing to do this, then we recommend that you ask those who can influence her to advise and warn her against the punishment of going to magicians and harming Muslims. If this does not help then her guardian - for example her husband - should be asked to prevent her from doing this. If she has no guardian, then the questioner should report this case to the authorities.
The questioner and his wife should shield themselves by mentioning Allaah the Almighty and reading the night and day Athkaar (remembrance of Allaah). They should also recite Chapter Al-Baqarah (Chapter 2 of the Quran) frequently. In fact, memorization of Chapter Al-Baqarah would be a very good thing for them. The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, urged us to learn Chapter Al-Baqarah. He, sallallaahu ‘alayhi wa sallam, said that there is blessing in memorizing it and sorrow in leaving it and that it protects against magicians. [At-Tabaraani]
And Allaah Knows best.