Most of the advices commented here are really too simplistic, as if this is a situation about whether to fix a shower or not. It’s true that you don’t owe your mother anything. And it makes complete sense that you have no idea how to handle this situation. As long as you feel that you don’t have that emotional capacity (and few of us would ever have that capacity, so it’s completely fine), don’t feel like being forced to make a decision. Heck, you don’t need to make a decision ever concerning this, because you in principle this shouldn’t be your problem.

But, as horrible as your mother is, part of the problem seems that somewhere in the back of your head you believe that she’s still your mother - no matter how bad of a person she was. A lot of people in our world suffer under great psychological issues, because they don’t have the strength to face a parent who did something extremely bad to you them. You never have to learn how to approve the decision that she made, because, as you rightly indicate, it cannot be approved of by any moral measurement. But if you feel that it’s important for you to get in contact with her again, then that’s something that people can only respect of you because it shows how incredibly strong you are. It seems to me that the fact that you ask for advice means that you actually have thought of the idea to reconcile.

This is easier said than done. Perhaps one way of being able to forgive someone who has done you so bad, is by seeking help. Ideally, you could go for therapy. But unfortunately that’s in many countries something only privileged people with money and time can do, so I’m not sure if it applies on you.

The most horrible thing in life is that people can do monstrous things - not monsters do monstrous things, but actual people do so. People who also have good sides, can do horrifying things to the people they are supposed to care about. That’s incredibly painful, and you learned by the toughest way I could possibly imagine.

So: Don’t listen to people who say: “it’s simple, cut her out of your life”. It’s not simple. Make whatever decision helps you to feel better about your own life. You don’t owe that to her, you owe that to yourself.