Be sure you have a come to Jesus meeting with the children, IF, they are of reason. Your grandma has been conditioned to think she is ok in adultery. We know this is against God's law. Grandma does not think before she speaks. We know better. We may have grandma for a while, for a meal, but we can't have her for long, for we do not want to upset the apple cart, the family.
Mother-in-law i has been brain washed in new order to think adultery is not adultery but having a friend and happiness is with human and not of God first for consolation. We see this in Sun City, AZ. It is bad! We know the new order is in accepting of immoratlities of all kinds. So, it is really sad. My mother went through the same. when my dad died age 54, 5 years later she marries a divorcee, recommended by my non religious aunt. My mother of the new order asked the new order, no priest what could be done for her to have it her way. Priest and mom had it rigged.Mom and divorcee were to get their relationship blessed (marriage) by a minister protestant. She did, at my Aunts house and my brother joined with his girlfriend double ring, double scandal. Then pay up front a $1,000 for this divorcee for an annulment, through new order. Then my mom could not receive sacraments till the annulment came back, approved (of course). Then the reason was, he did not know divorce was wrong. (sure?!) Then she could go to confession and all would be in place, or look good.
So, my mom did not like me, but I told my other 8 siblings, oh, well. There is nothing catholic going on there. Really sad!!