Hi, I'd like to help you with your question.
The dilemma for adults who are abused as children is how to handle their relationship with their parents, especially if the parent or parents continue to be abusive. The guilt about being a good child and having a relationship with the abusive parent makes it a difficult struggle.
You deserve to be treated with respect and kindness. If your mother was a stranger, co worker or friend that treated you that way, you would end the contact and stay away from that person. Being your mother does not give her the right to continue the behavior.
It is just fine to cut off contact. It is actually very healthy to do so. The problem comes in with how you handle the emotions you feel as a result of removing yourself from the abusive relationship.
Having the strength to deal with your mother is good, but that also leaves you with a dysfunctional mother and no real relationship. Therefore, it is important that you mourn over the loss. You want and deserve a normal relationship with your mother. But since she will not allow it, it is a loss. And it is ok to feel sad and upset about it.
Keep your boundaries with your mother. She may never see that she needs help, but that does not obligate you to have a relationship with her. The relationship you would have with her just results in more hurt and pain for you. And your mother needs to learn that you are an adult now and she can no longer hurt you.
Also, it may help you to go to counseling to talk about how you feel. If you feel the social worker is not helping, it is ok to seek out another therapist.Talk to your doctor for a referral or if you attend church, your pastor can help. You can also search on line at http://therapists.psychologytoday.com/rms/.
Here are some other resources that may help you as well:
Adult Children of Abusive Parents: A Healing Program for Those Who Have Been Physically, Sexually, or Emotionally Abused by Steven Farmer
Toxic Parents: Overcoming Their Hurtful Legacy and Reclaiming Your Life by Susan Forward and Craig Buck
Healing the Scars of Emotional Abuse by Ann McMurray and Gregory L. Ph.D. Ph.D. Jantz
I hope this helps you,