Is it permissible to sever ties with a mother-in-law who accuses her son's wife of immorality and sorcery?

The paternal aunt (ammah) is a relative with whom connection must be maintained, and severing ties with her is forbidden by scholarly consensus. Severing ties of kinship is among the major sins. The aunt's ill-treatment does not permit severing ties with her, because maintaining kinship ties is not a matter of reciprocation. However, if maintaining ties with her results in definite harm, then there is no sin in severing ties. You must be patient with your aunt's ill-treatment and seek reward from Allah. Whoever maintains ties with those who mistreat them, Allah will help them against them. Repel the evil of those who mistreat you with good.