I had a similar childhood but different to yours, but the same outcome. I was fine until I had children of my own and realised how truly grim and sad my own childhood was.
Have you had therapy with a counsellor or professional that specialises in childhood trauma? Having this time to talk through my childhood was so helpful to me op, and helped me understand what happened then, and what is happening now.
Your mother is in denial, she is in denial because she would not be able to live with easily with what she did, so she protects herself from the truth. This is to enable her to carry on, but it denies you the recognition and acknowledgement of what she did, and the impact it had on you. That is very hard to live with, the silent truth, unspoken.
Find someone else to talk to about your childhood, work through your own emotions towards her, and keep your boundaries in place. She hurt you a great deal op, by the sounds of it. You don't have to have a very close relationship with her. Your dc only need a good and happy mother, good gp are just a bonus if you have them, not an essential requirement.
I am LC with my mother, I see her on my own terms and in a way that makes me feel healthy and well. I don't talk about the past, or about the future. I keep the conversation light and fluid. I have a slightly different set up to you - but I would think carefully what kind of values she is passing on to your children - are they the ones you have chosen or she has chosen? Are you happy with the interaction and the contact?
Always have an alternative plan B with a mother like yours, that does not rely on her keeping her word or being there for you.
The best comfort we can take is that we are by far better parents that they will ever be, we have broken the toxic cycle for our own children. We have cracked it, and you should be proud every day of the childhood you are giving to your little ones. Watch out for triggers, watch out for your self care and not over giving - and enjoy your life now you are free of all the things that held you back as a little girl 