For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because you have rejected the word of the LORD, he has also rejected you from being king.
1 Sam. 15:23

Gal. 5:
Now the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God.

The point of these is that if you practice witchcraft you are an enemy of God and subject to the vices of fallen angels. All the more reason there is strife in your house.

I suggest repenting turning to Jesus, and using the power of God to disarm any satanic influences your step mother may be manifesting.

You may actually have to forgive her. This is the hard way, but the triumphant way of Christ.