Hi, I'd like to help you with your question.
It sounds like your mother may have a personality disorder. These disorders cause a person to have trouble relating to others. So instead of reacting in a normal way to something, they try to either twist it around or lash out.
Personality disorders is a group of disorder that can include many different symptoms. Here is a link to help you find the symptoms your mother may have:
Unfortunately, as you have discovered, people who have personality disorders do not have insight into their own behavior. They either claim they are not doing what others tell them they are doing, or they twist it around to blame someone else. Therefore, they usually are not open to seeking treatment. If nothing is wrong, why see a counselor?
That leaves it up to the family to find a way to cope. Coping with someone who has a personality disorder can be draining and stressful. There is no way to relate to them normally so you either are on the defensive or you become frustrated and angry.
What you can do is learn more about personality disorders and how to respond to your mother. In addition to the link above, here are some other resources to help you:
Difficult Personalities: A Practical Guide to Managing the Hurtful Behavior of Others (and Maybe Your Own) by Helen McGrath PhD and Hazel Edwards MEd
The Cognitive Behavioral Therapy Workbook for Personality Disorders: A Step-by-Step Program (New Harbinger Self-Help Workbook) by Jeffrey C. Wood
You can find these books on Amazon.com or your local library may have them for you.
You can also consider family therapy. Your mother may or may not go, but talking to a therapist about how you can address your mother's behavior can help you cope.
When you deal with your mother, try keeping your tone and responses as neutral as possible. If she does have a personality disorder, this will help keep the yelling and screaming down because she has less to respond to.
Try to see if your mother will see her doctor. Along with a checkup to be sure this is not physical in cause, you can call ahead to the doctor and let him/her know about your mother's outbursts. They may be able to get her to listen and get help. It often has more impact coming from a doctor than family.
I hope this has helped you,