DEAR ABBY: My brother-in-law passed away six months ago, and my mother-in-law, “Grace,” is understandably grief-stricken. My husband and son have been very supportive of her. My father-in-law passed away nine years ago. I have tried to be supportive as well, but Grace and I have always had a contentious relationship, and she really wants nothing to do with me. The problem is, my husband and son ha…