I was hoping that I might be able to be a liaison between my fiancé’s mother and my fiancé, but having spoken to his mother this morning, I am not sure how welcome that will be. She said that I might be able to call her every six months or so and that it is all scripturally based
You could continue to try to go down this track. There is no reason scripturally why she can't talk to you often. You have never been a JW and those rules do not apply to you. You could tactfully ask her about this, as well as expressing your desire to get to know her better