Is the husband sinful if he cuts ties with his mother after she has harmed his wife?

Your husband's mother is oppressing you, and it is incumbent upon your husband to provide you with an independent dwelling and to gently and politely forbid her from committing evil deeds, without harshness or abuse, for the matter of parents is not like that of others. It is not permissible for him to sever ties with her, even if she is unjust; rather, he should advise her kindly. He must also hasten to repent to Allah and strive to be dutiful to his mother.