Ahhh!!! I’m so sorry to hear that! I’m in a very similar boat myself. My mom didn’t change my ways until I stopped biting my tongue with her AND her husband (my step-dad). Due to childhood issues I finally wrote my mother a letter (in lieu of talking because she interrupts, doesn’t listen, and gets defensive) and - long story short - there was not the support needed for me to trust her with me or my kids. I haven’t talked to her in a couple years and it’s been the most peaceful time of my life. I had talked to my brother about it all in advance and he was supportive so he and I are still in contact. So I guess my advice is … We can’t make others change their ways, but we can change ours. We can can’t choose family, but we can choose what we do with them.
I don't have much advice to give but I want to encourage you to continue breaking the cycle! It's so hard to do but the fact you are aware of the negative impacts and actions of your mother means a lot in your own growth! Your child is blessed to have you and your gentle approach! Keep up the good work momma! Do what feels right for you and your child.
Have you two tried talking about the issues you have? The 25th of January is a long way away! Maybe call and vent to a friend a couple times a week to keep yourself sane? I think we can easily revert back to how we were as kids when around our parents/family. Try to be as aware of that as possible and keep parenting in the way you want.