What is the ruling on keeping the relationship superficial with my future mother-in-law, who thought ill of me and was verbally abusive, while being keen to encourage my fiancé to honor her?

It is advised not to expand in dealing with the suitor because he is a stranger. As for dealing with the suitor's mother, there is no objection to being reserved and not expanding in dealing with her, but it is better to treat her kindly and overlook her shortcomings, for forgiving those who do wrong is a noble trait, and responding to bad deeds with good ones brings affection and protects against the evil whispers of Satan.