"I can't keep dd away from her that would destroy her, she loves her. Sometimes too much like she thinks she's hers"
Her behaviours towards you and by turn your DD are not loving at all.
That sort of love is unhealthy and smacks more of power and control. She will inflict the same sort of harm done to her as has been done to you. Do you think she is a good grandparent figure to your child bearing in mind she is not a good parent and never has been to you?.
A percentage of the general population is dysfunctional and/or abusive. That percentage, like everyone else, has children. Then those children grow and have children of their own. The not-so-loving grandparents expect to have a relationship with their grandchildren. The only problem is, they’re not good grandparents.
Many adult children of toxic parents feel torn between their parents’ (and society’s) expectation that grandparents will have access to their grandkids, and their own unfortunate first hand knowledge that their parents are emotionally/physically/sexually abusive, or just plain too difficult to have any kind of healthy relationship with.
The children’s parents may allow the grandparents to begin a relationship with their children, hoping that things will be different this time, that their parents have really changed, and that their children will be emotionally and physically safer than they themselves were.
Unfortunately, this is rarely the case, because most abusive people have mental disorders of one kind or another, and many of these disorders are lifelong and not highly treatable. (Others are lifelong and treatable; however, many people never seek the necessary help.)
The well-intentioned parent ends up feeling mortified for having done more harm than good by hoping things would somehow be different — instead of having a child who simply never knew their grandparents and who was never mistreated, they have an abused child who is now also being torn apart by the grief involved in having to sever a lifelong relationship with the unhealthy people they are very attached to.
Do not become that well intentioned parent; the road to hell is laced with good intentions.
Re your comment to Cailindana:-
"Cailindana - I can't give up on her I just want to fix it I can't accept its unfixable. I can't seem to keep friends b/c I have huge confidence issues"
There is nothing to fix here because your mother does not want to be fixed. You are her DD; not her therapist or counsellor. She never sought or wanted to seek the necessary help; you yourself wrote that her own childhood was awful. That is not at all surprising given her behaviours towards you now and back then. This is how she wants to be; she sees nothing wrong in her behaviours.
Your mother's actions has given you huge confidence issues. You were probably never encouraged to speak out or to ever have friends. Your mother also thinks she is fine; you will not ever get past that wall of her own denial.
You cannot change her; you can only change how you react to her.
Your other siblings have backed well away from your mother; you ultimately need to do the same.