My 83-year-old mother is jealous of my 18-year-old.

I searched for some online help and ended up here. I am so grateful to find this community. I have read many of the situations here, but I did not find one quite like mine. In August of 2016, my 18-year-old left for college. Later that month, my 83-year-old mother began to spend her nights at my house in my absent daughter's room, because my mother's roommate was in the hospital and she didn't want to be alone at night. Logistically, that worked because I lived just a few minutes from her. In November the friend died and Mom moved in permanently, using my daughter's room as a temporary place. In December, my daughter came home and being the sweet child that she is, she was happy to give up her room and sleep on the couch for her grandmom. However, during my daughter's stay, my mother's behavior became increasingly disruptive and by Christmas and New Year we felt like we were in a war zone. My mother was combative, everyone was against her, no one loved her, a lot of her problems seemed to center around meal times. She claimed she wasn't eating like everyone else and it just was not true. And she did not like the fact that my daughter got attention from others because she was home for the holidays. Mind you, everyone went out of their way to make Grandma feel loved and happy and included, but the more everyone tried the more combative she became. Once my daughter went back to school, viola, the world was right again and my mother calmed down. I took her to a neurologist, they said she was fine after doing the blood work, MRI and x-ray workup. In an attempt to fix things, I had the bright idea of moving my family to a home where everyone would have a room and so, between January and April, I did the impossible. I found the perfect house in the perfect neighborhood and we moved. Mom was so happy with her new room. She got the bed she wanted, she got the furniture she wanted, she could decorate her own room the way she wanted. All was well. We were happily in the house for 2 weeks and my daughter was scheduled to come home the next day. As I hurried to put some order to my daughter's new room, my mother began ranting, "Why are you doing that?" "She can do that herself." "You are doing too much." "She needs to do more than just sit and look pretty." "Stop moving furniture by yourself." "You are just stupid and crazy." I was shocked and appalled at my mother's actions. By the next day when my daughter actually arrived, my mother had completely reverted back to Christmas Grandma, only this time she was worse. Nothing was good enough, no one loved her, the dog even turned against her in her eyes. She ranted and raved, hollered and screamed, cried, slammed doors and wouldn't eat at times. I mean she turned into someone who I could not stand to be around. I have never talked disrespectfully to my mother and I told her finally to "SHUT UP!" My daughter, who is the sweetest child on the planet, could not understand why her grandmother appeared to hate her presence. I had told her how well Grandma had adjusted to the new place, only for her to come home and find her acting like a lunatic. Grandma never stopped ranting and raving the entire time my daughter was home. My daughter ended up being sick and spending most of her time home in bed and of course, when I took her tea or medicine I was ridiculed. My daughter stayed home 2 extra days because her fever was so high and she just felt too bad to get on a plane. Today, I took my sick child to the airport she had to go back for a test tomorrow. My mother did not say goodbye to her she just ranted and raved about no one doing anything for her. One more thing I want to add is that my mother did not smile the entire time my daughter was home. To my dismay and frustration, I arrived home after dropping my daughter at the airport and my mother greeted me with a smile and telling me about a pill she just heard about for the dog for allergies. My thoughts were, "Really Mom? Are you serious that for 6 days you could only rant and rave about nothing and once my child is gone you are ready to talk about a pill for the dog?" But I said nothing. Now she is back to normal as if the past few days did not exist. Today, I made appointments with the neurologist and her primary doctor, but I am sure she will smile and look so innocent that they will think I am the culprit. Here is the problem and where I am seeking advice. My daughter will be home for the summer in just a few weeks. I don't know what to do. If my mother carries on like this for the whole summer we will all be nervous wrecks and she will probably cause herself some physical harm. I almost called 911 yesterday because she had worked herself into such a frenzy that I thought something might happen to her. She said she was leaving, packed and threw bags down the steps and I really thought she might collapse. Of course, she did not leave and I had a mind not to stop her but I did. But now summer is near. Any thoughts?