It's a great accomplishment to come from a dysfunctional background and rise above it. Being mentally healthy and raising your own children to be successful human beings is something you can take satisfaction in. Your sister is who she is and, at age 71, is unlikely to change very much. You can't "repair" a relationship with her. If you're thinking you'ld like to take all the anger that you've stuffed and verbalize it to her, then I think you do need to see a therapist. You need to get to the bottom of what's really bothering you. You're not "furious" because your sister has been a lousy parent, as I can easily believe she has been. What did your sister do to you that you so deeply resent? What were the problems in the home that she and you grew up in? That might be something to explore in therapy.

You've portrayed your sister as the matriarch of a family system that is a complete mess. I believe you. But I feel like I'm not sure what your main point is. I have a sibling who is a complete mess. I could tell you how he drinks and drugs and goes in and out of jail and prison and has terrible relations with people. But those are his problems. I've learned I can't do a darn thing about them. It may be you need to separate yourself mentally from the dysfunction of your extended family.

There is no having a healthy relationship with someone like your sister, or your nephew, or your grand-niece. I've had to accept that there is no having a relationship with my brother that isn't crazy-making for me. In the case of some people, all you can really do is lament the waste and calamity that their lives have become and move on with taking care of what it is your business to take care of - your own life, your own immediate family.