What you are describing could be the behaviors of someone with Borderline Personality Disorder. BPD is characterized by unstable relationships and emotional dysregulation. Fear of abandonment often fuels emotional turmoil. I suggest you read up on it and see if it fits.
If so, all you can do is love her and be clear about your own boundaries. When she calls, don’t try to reason with her or to defend your life. Don’t take sides in her complaints or arguments. It won’t change her and will only make you more frustrated. Just tell her you are sorry she feels the way she does; that she knows in her heart that you love her; and that you will talk to her when she is able to be calm. If she can’t calm down, tell her you have something to do and you’ll talk to her later. Then politely hang up.
It sometimes helps to set a time when someone like your mom can count on hearing from you. You might make an arrangement to call her, say, every Sunday evening at 8:00 and guarantee her an hour. Let her know that you are happy to have a good chat at that time but that your life is too busy to call her in between. Politely end the call after the hour is up, no matter what is going on. By compartmentalizing the calls, you give her something to count on and you give yourself room to get on with your own life.
You can certainly share information about BPD with her but she may not listen to that any more than she has listened to other things. Dialectical Behavior Therapy (DBT) has been found to be very helpful for people who carry that diagnosis. You might want to find out if there is a DBT therapist near her in case she is open to getting treatment.
I wish you well.