OP, many years ago I read an interview with Noel Gallagher of Oasis.
His father was a horrific sociopath who abused him, his older brother Paul and their mother. Everything from violently asaulting Noel, destroying their possessions, eroding their mother's self esteem and forcing her to work 3 jobs while he spent his wages on booze.
He once called their mother one evening when she was at her factory shift job and told her if she didn't come home right then and there, he'd set fire to their house and kill baby Liam and little Noel. (When she got home, the boys were alone in the house and Gallagher senior was nowhere to be seen - he'd left the boys after the phonecall to go down the pub on a bender. Didnt come home for days)
Noel was no-contact with his dad since the day their mother packed a bag and fled the home with the kids. But he said people would ask him why. Surely his dad wasnt that bad? But- he took you to Manchester City's football stadium to watch them play!!!!!
Noel's sarcastic response was something like: He wasn't such a bad dad after all, eh?
Please don't feel you have to explain away your decision. It's something that must be gnawing away at you now she's older, and ultimately it is your decison whether or not you want to be involved in the future... but you owe her as much as Noel owes his dad. Nothing.
A parent has one job. One. There is no excuse for a parent to abuse their child. Not one. Not trauma, not mental illness or ill health, nothing. When you empathise or sympathise with someone who has hurt you repeatedly, you are playing into the abusers' scheme. They don't deserve a shred of it.
You are a truly wonderful, phenomenal person to have made it into adulthood with your empathy intact and your ability to still care/have concern for your mum... but you deserve better than being drawn back into an unhealthy dynamic.
Take a leaf out of Noel's book. Put yourself first. Don't sacrifice yourself and all the hard work you've put in.
And fuck the tossers online or elsewhere who might judge you or play the old 'but she's your mum' card.
They're almost always narcissists or bullies themselves, filled with horror at the thought of an adult child who broke away and stopped the cycle. That's how narcs and abusers reproduce, so naturally they want to shame and bully people who have ended the cycle.
All my best wishes to you. 🩵 Listen to Oasis' Live Forever... 'lately I don't really wanna know how your garden grows, 'cos I just wanna fly.'
Take the advice, don't let the past try to get its grubby hands on your self esteem. You're worth every inch of the freedom and the life you've built for yourself.
**(there's a lot of wisdom in Noel's very Irish-Mancunian brand of musical melancholy).