Hi, I'd like to help you with your question.
First, I am sorry to hear what you went through as a child and continue to deal with in your family. Child abuse is so damaging to all involved, but particularly to the child herself.
It sounds like you have done a wonderful job using what happened to you and turning it around and raising your children with love and security. What a great testament to your strength as a person.
Keep in mind that you did a great job raising your children. You gave them all the things you did not have and now that they are young adults, they need to use what you gave them and find their own way. It sounds like your daughter wants to understand where you came from and what your family dysfunction is about. Finding out that information has to be a shock, even if it is inaccurate. She needs time to understand it and sort it out. She is also very young and may not completely understand the way people can act when they are hurting or damaged in some way emotionally.
Have you tried talking with your daughter directly? Was your childhood ever a brought up while your children were growing up? If they had no information about your childhood before, this will be completely new to your daughter and she may not have any idea of what to believe.
Talk with her and tell her that there was abuse in your background. Let her know that part of that abuse was emotional, which included manipulation. Let her know that sometimes in an abusive family, there is one child who is targeted and that child was you. Tell her that she will hear things from your family that may not be true. This is because those members of the family have not come to terms with the truth and that part of abuse is using mis truths in order to continue the hurt.
At this point, after you have told her your side, you can let her know to come to you with any questions she has and that you hope she will talk with you anytime she needs to. Then let it go. If she is hostile, try to be kind to her but don't try to defend yourself. Just tell her the truth and let her sort it out. It may take a while, but with maturity and understanding on her part, she will eventually come around.
If you do chose to have your mother help intervene, you may want to be there with her when she talks to your daughter, if you feel ok doing that. It will help prevent misunderstandings and help your daughter see that you are willing to be with your mother and try to work things out.
You also may want to consider therapy for yourself and if you feel it is needed, go with your daughter as well. Letting a neutral person help you sort out all the pain and consequences of your childhood can help you get a clearer picture of how to help your children respond as well. You can ask your doctor for a referral or if you attend church, your pastor can help. There is also a link on line at www.find-a-therapist.com.
I hope this has helped you,