My MIL is 80 and has started being a very jealous person. Putting pictures of my husband's wedding with his ex out on display so I will have to see them. Also put a senior portrait of her many years ago as she graduated from high school. She hasn’t came right out and accused me of having something for my father in law but has done everything but that.
You are smarter than a woman with a broken brain. Now, all you have to do is figure out how to let all the aggravation roll off of you, which is easier said than done.
Start looking into Memory Care Assisted Living homes now, so when the time comes that MIL becomes too much to handle, you'll have Plan B in the bag.
Best of luck!