I had CBT to help with my low non existent self esteem and trauma therapy to help with some c-PTSD symptoms from my childhood, and I did a lot of reading!
My DH is absolutely incredible and has patiently listened to me talk and digest things a lot - he had a positive, balanced childhood and really just being reassured that the dysfunction wasn't 'in my head' was a huge help.
A big turning point was me actually going no contact after she fell out with me for the umpteenth time (she was being very unreasonable and controlling). A year of being able to just get on with life really, really helped.
I did reach out to her after that year and we then talked a few things through, but I had to word things very carefully. For example, instead of "you were a shit mum" I would say "I don't think you had enough support to be the best mum you could be, but what do you think?"
And she would reply with "I found it very lonely, stressful and I wish I had been more patient with you."
Acknowledging her own impatience was huge and I would reassure her I had no resentment or blame, that we all look back and wish we could do things a little better. Over time, we talked more and she remembered more. Once she phoned me in tears because she remembered an incident where she had been violent (but blamed me). She realised her actions were pretty bad and I'd done nothing wrong. It helped hugely to have this recognised and we both could move on.
I imagined her as a child, and that helped dissolve a lot of resentment I had. And I'm so surprised that over the years she's just blossomed into a supportive mum.
She's always going to be a bit unstable, sensitive and prone to wanting to control and there will always be a part of me that wished things had been easier, but (as I say to my mum now) it's all about looking ahead, looking forward. There's nothing we can do about the past but we can definitely make the present as good as we can. But boundaries, boundaries, boundaries! This has been the key thing.
I really hope you can forge the relationship you would like, OP. There is hope!