What to do with a narcissist mother?

My mother is 82, healthy and fairly active. However, she has always been a narcissistic person & is getting even more so with age. Everything has to be absolutely her way or it's no way. My brothers & I have had a lifetime of this behavior and my poor dad just goes along with her to get along. She still manages to make his life hell. On the Monday before Father's Day, my dad's brother passed away after a brief illness. We were all expecting it and had been visiting with him in the weeks leading up to his death. My uncle had arranged to donate his body to science and would be cremated after. He wanted no funeral, no memorial. With Father's Day approaching the following Sunday, my mother told me she wanted to cancel the get together my brothers & I were planning for my dad. I asked her why would she want to do that when it would mean so much to my dad. Our plans remained even though she was in a snit over something else (my dad's sister had upset her). I asked my mother to put aside her hostility because my dad had lost his brother and in the process, it appears that he will be losing his sister as well. He needed this celebration. She agreed, although reluctantly. One of my brothers and his family were coming into town to spend the night with them but called my mother to tell her they would need to leave early in the afternoon on Sunday, so we could have a Father's Day get together on Saturday night instead if it was okay with everybody else. I should mention I just live down the street from my parents & it was okay with me as my daughter was coming in on Saturday as well. The other brother wasn't going to be able to make it until Monday. My mother was absolutely furious and pretty much told them to stay home and not bother with it all. My brother told her they wanted to come into town to spend time with our dad & if she didn't want them to stay at their house, they would stay at mine, as I, too, have plenty of room. In the meantime. my brother called me to tell me about this but also said he didn't really know what to do because if they stayed with me, he thought it would fan the flame, so to speak. I agreed and he said they would go to her house and see how it goes but left their suitcase in the car just in case their reception was hostile. I prepared dinner for everybody, made margaritas and a really nice dessert. She didn't show up. After dinner I drove up to her house where I found her just sitting on the porch, drinking Bailey's & coffee and smoking her cigarettes. I asked her if she wouldn't please reconsider and come back with me to have dessert or at least a drink and play cards. Nope, she wouldn't do it. "Just tell your dad to get home in time to give the dog his shot." The dog is diabetic & takes insulin twice a day. Since my mother was not at all happy with my brother for needing to get home a few hours earlier than she wanted them to, she told them they would need to get up and get out by 10:00 as she was going to the casino (about an hour & a half away). So rude, but she was going to show them just who was in control apparently. My parents usually go to the casino once a month or so, but they had already been the previous week. That's why I knew this was just another one of her stunts. My sister in law sent me a text telling me my mother had taken all their pictures associated with their family down from the walls in the guest room where they slept. She had even taken down the picture of their great grand baby. She asked me if I had noticed the picture of some kids prominently displayed in a frame in the living room that said "Grand Kids". Oh yes, I had seen that and also how my mother even said she feels closer to them than her own grand children. Another story altogether. My mother's antics definitely marred the celebration for my dad. He just sort of rolls with the flow and is probably so used to her behavior, he barely acts like he notices. It is very disturbing to us, however. When my brother and his family were leaving, she asked them if they were still planning to come for the 4th of July. My sister in law was somewhat flabbergasted & simply replied she would have to let her know. I can tell you if anybody had treated my mother the way she treated my brother and his family, she would probably never speak to them again. Of course, now my mother has realized she screwed up on some level, but only offering excuses, never apologies. She is always the first one to demand an apology but has yet to apologize for anything she does. Instead, she tends to deflect or gloss over. My brother is offering her a way out of the hole she has dug for herself by choosing to forgive & forget and that is very gracious of him, but these little tantrums she throws are getting so old. Since I live just down the street (since last year & a move I have come to regret), I get to see more of them and no luxury of distance between us. Any suggestions on how to deal with the narcissist person?