You need to decide how much you do not want her in your life. I’m your age with younger children, the best thing I ever did was go NC with my mother. My DCs were upset, they missed her at first but it was worth not having them in both mine and their lives. My youngest dosnt even know who she is.
My M is the opposite of yours, she couldn’t give a shit about me being in her life, in fact she’s done her best my entire life to make sure I was left out. It only took a couple of not answering her calls for her to be offended and stop trying. I did get one text to tell me someone had died, I knew if I’d answered it I would be sucked in. After that I blocked her number. She’s blocked on social media and I made sure she’s blocked on my DCs accounts. Officially they are too young for social media (oldest 10) but they have accounts I set up during lockdown so they could chat to their friends, they still use these. I set them up under their nicknames which my M knows and I wouldn’t put it past her to try and make contact so I’ve made sure she can’t.
I’ve been 100% honest with my DCs why I’m NC. If they choose to have a relationship with her when they are older that’s fine.
After my DF died my M tried all the guilt laying shit about how she would need to lean on me and need me to step up and be there for her, never mind I had 3 children under 6 including a newborn baby and absolutely no help from anyone, she expected me to support her even though she’d made be feel like an outsider my entire life, I don’t fucking think so. I’d spent my entire pregnancy (at 41) running round, which I was happy to do for my TI DF, that included spending time with her to give him a rest. None of my precious siblings were to be seen, these are the golden children (well one is, the other is when it suits, now my DF is dead my DBs bank account very much suites her), and my siblings are quite happy to exclude me because it’s less aggro for them where she is concerned. For some reason they think I’m ok with this, I’m not but I’m beyond caring and I have made the decision to just get on with my life without any of them. My life is so much better now.
You can get counselling through minds matters, I did and it as amazing.
If you really do want her out of your life, you have to stick to your guns, block her number, get a restraining order if she turns up. Even move if you can. I’ve moved since I’ve gone NC and it’s such a weight lifted knowing there is no chance that one day she will show up as she has no idea where I am.