Well, maybe a good way to tackle the anxieties you (quite rightly) still have over your MIL's behaviour would be to talk to your DH and ask him to speak to her.
It is relevant, as it's clear that this is ongoing for you - which is an absolutely reasonable reaction to what she's done!
Would it be an idea to sit down with your DH and spell out to him that you now know, now that time has passed, that what she has done has actually driven a huge wedge between you. You feel on edge and cannot trust her. This is only compounding the ongoing anxiety you feel, the out-of-your-control aspect of the whole situation. This is wrong. At the time you felt so awful about it that you couldn't confront her properly, but you now know that for things to have a chance of being right between you all, you need to KNOW that she understands a. that what she did was seriously, majorly bad and b. that she is actually now lucky to be in your lives and that further contact with your mother would result in you having to cut her off.
If your DH would now (not in anger, but calmly, now that time has passed) be able to sit down and make this clear to her, maybe this would not only help your anxiety but give you a bit of the 'power' back in this situation.
You could also ask DH to ask her why she would want to hurt you all like that, to put her own grandchildren in touch with an abuser. Shock her, make her think about that.