Hello, I'd like to help you with your question.
It does sound like your mother might have a personality disorder. When someone acts as she does towards others (idolizing certain people, demonizing others, etc) and is not able to regulate their emotions in order to get along with others, it is possible they have a personality disorder.
Personality disorders are typically ingrained behaviors that someone develops, usually in response to being raised in a dysfunctional home. The person could not get their needs met (for unconditional love and attention) so they developed other ways to get what they needed which usually involved dysfunctional behaviors. When they grew up, they continued these behaviors even when they were no longer needed.
Knowing what your mother might have and how to react to her behavior can help. While there is no way to diagnose her without seeing her for an evaluation, the behavior you describe sounds like narcissistic or borderline type. Here is a link that can help you figure out what she might have:http://www.nmha.org/go/information/get-info/personality-disorders
Many people can have some traits of one personality disorder or they can have some traits of a couple of personality disorders. By finding a personality disorder that seems to fit, you can at least know what you might be dealing with.
When dealing with someone with a personality disorder, it is helpful to keep in mind that they are not reacting to who you are as a person or even what you are doing. They are going by cues they learned long ago on how to relate to their world. And their responses can seem overwhelming and out of touch with the actual situation. They can also be very hurtful and hard to cope with.
If your mother won't get help or change in any way (common with someone with a personality disorder), you may have to change how you interact with her. One thing that helps is to see what she does as about her own issues and not you. Also, think of one phrase you can say to her that neutralizes anything she might say. such as "I'm sorry you feel that way". That usually shuts down the person and you can make a quick exit out of the situation.
I hope this has helped you,