You know what? You recognize that there is a problem with your relationship with your daughter so, there is a lot of hope for this problem. Follow through on your therapy plan so you can have a better relationship with your daughter than your Mom obviously has with you.
How is your relationship with your Mom now? How is the relationship between your daughters and your Mom? Is there a difference between them?
I am sorry that your Mom was not there for you when you needed her. Your Mom was wrong for the way that she handled the situation. Do you have a lot of angry towards your Mom and your daughter reminds you of that?
Don't give up. I am glad that you are going to get help. Your daughters deserve to have a great relationship with their Mom.
By the way, all kids think their Mom's are mean at one time or the other.
I am in the process of seeking outside help because it is killing me that I am harder on her. Her birth is not what I expected. I know a preemie birth is not what anyone expects but my mom made it harder. She put down my doula, she came into the delivery room and held my daughter before I did. I felt so detached at that point. Like this was not my kid. After I came home my mom put me down and made me feel inadequate. I even cried and yelled that if she could quiet Emma then maybe she should take and keep her. I was suffering PPD as well. My mom just looked at me and with a wave of her hand and smirk said get over it. So much to deal with.
With my second daughter it was only me and DH in the delivery room and afterwards. Not to mention we moved to FL and mom was in NY. I bonded with Erin so fast and know I am more in tune to her. It hurts me so bad.
I think you need to seek some counseling-- for the family, and for you. The most important thing that a mother can give to her children is the confidence in herself that she can take care of them. It sounds like you need some help for yourself to get your confidence back , and that will help your family in the long run. Until you solve that problem, anything else you do will probably not be effective.
Good luck.