Hi, I'd like to help you with your question.
The symptoms your mother is having could fit many different disorders. It is hard to say for sure what it could be without more information. But I can try to help by giving you a idea of what it could be based on what you told me.
Is your mother willing to see her doctor for a full exam? You did say she had an MRI, but it may be that she has something else that is not related to her brain function. If she is willing to go to see her doctor, that would be a good first step. Therapists often recommend a full exam first before offering a mental health diagnosis because so many physical problems mimic mental health disorders. Early onset dementia is one example. Thyroid problems and other hormonal imbalances could also be causes.
If your mother is cleared by her doctor, then she may have a mental health issue. A full evaluation by a therapist (Master's level or Ph.D) can determine if there is a diagnosis and if so, what treatment is needed.
Some of the possible diagnosises include Bipolar, ADHD (adult onset, which would mean she has had some symptoms from childhood) and anxiety. Without being able to talk with her, these disorders are only guesses on my part. But each of these disorders have some of the symptoms you described. That does not mean your mother has them. It is highly unlikely that she could develop them at her age, except for anxiety, which can be developed at any age.
The trigger here could be your move out of the home. Were you and your mother very close? Were there any recent traumas in her life? Anything you feel might have triggered a reaction is possible. She could have developed an anxiety disorder due to a traumatic change in her life.
The most important step is getting your mother to go to see her doctor, and if needed, a therapist. Both examinations will help solve the problem and get her the right treatment.
Let me know if I can help any further,