Any advice on how to forgive?

Are the children under 16?
If so I can see that you may not be able to fully disengage from her.
But I think either way you just have to side step.
Remember the old saying
Don't wrestle with a pig
You'll both get dirty but the pig will love it.

I suggest you delete any way she has of contacting you. If you are hearing second hand, tell the person you don't want to know. If it's your son, suggest gently that he goes for counselling as an independent person might be better. You don't need to forgive, just be disinterested

Ignore that last message I used to be Florentina1

I have not received it.I think by my user name it has gone to a
Old account to a dead email Please will you try and send it again

It depends what you mean by "forgive". My ex-dil was exactly like yours. I could never say I forgive her if she took that to mean that what she did does not matter and she doesn't have to feel bad about it. If she sincerely apologised and tried to make amends I might feel differently - but she's not likely to do that. I have however decided to stop letting what she did affect me.

Have sent you a PM.

I could have written your post word for word. Fortunately my son was able to escape but not without considerable damage to him and the children.

I don’t find it necessary to forgive as the harm was not done to me. I don’t believe she was evil just sick.

You cannot forgive unless she comes to you , expresses remorse, and asks for your forgiveness.

It is possible to be philosophical and say " none of us is without fault " but this is intellectual not emotional.

Your best strategy is to think about someone or something else and get into the habit of doing so.

Write a letter to her, telling her exactly what you think of her. Take a match and burn it (—making a wish while you do it.🤭—).

As hard as it is to do, I think you have to just bag all the anger, hurt and injustice up and dump it into the rubbish bin of your mind. She's probably not in the slightest bit bothered about the chaos she's caused, these people aren't, whereas you are left with the fallout. The good thing to come out of it is that you have managed to mend some relationships.
For years I was in turmoil over how my brother had cheated me after our father had died, he being executor of his will. I was not only angry with him, but with my father for not making me co-executor which would have made it difficult for my brother to do all that he did.
I realised that this anger was making me ill and I had to make a conscious effort to stop, accept it was all in the past and there wasn't a thing I could do to change what had happened. My brother died last year, so even if I wanted to, we couldn't reconcile.
You just have to accept what happened and get on with your life, the alternative is to live in angst and misery. I wish you well LR

Enjoy and make the most of the life you have LR10. Be thankful that your son has finally become free of her and that he and your GC are still a part of your life.

As anna has posted she's your son's ex so leave her in the past.
Forgiveness may come with time, it may not but either way, don't let thoughts about it consume you .

Have you looked at a ritual called Cutting the Ties That Bind.. by Phyllis Krystal.. you can google it.. that might help you to move on..

Why do you need to forgive? You don't need to bear a grudge but if she is now your son's ex wife just move on and leave her in the past.