I guess I will never understand why children always want to beat a dead horse when it comes to their family. It took me a really long time to distance myself from my abusive mother, but I finally broke free. She died and I was relieved and happy. I never confronted her, the fear was too great, but she had to have known what a crappy mother and person she really was.
If confronting her will help you, then go for it I guess. But, at some point you will have to accept what she really is...probably a narcissist and someone who shouldn't have procreated.
As a parent, I love both my daughters equally and I believe most "normal" parents feel the same. Yours didn't love you that way and I am sorry for you. But until you accept the fact that you can't change the past and the future with them looks very bleak, you will not be free to love and live your remaining life happily.
I don't mean to sound cruel and I hope you can see where I am coming from. I wish you all the best in eliminating this source of pain from your life. I don't think therapy will fix this, but it may help you to find a resolution to your angst.