I find this scenario sad.
I think you are in a good space – especially if I go back to your thread from September. Be aware that you are healing, and don’t allow her to drag you back into a negative space. Your best way to deal with her is to accept and constantly remember that you can’t control her, but you can control what impacts you. Her relationship with her sons isn’t really your concern OTHER than how it might impact your sons.
However – the key issue is that your sons are in their 20’s, and therefore should be capable and able to decide themselves what interaction they want with other people – parents included. I have said this several times on this site: Our parental role changes over time, and part of that role becomes where we step aside as controllers and become advisors and spectators. Like we might dictate what bike a 5 year old gets, prevent wrong purchases for a 12-year-old, and advise a 25 year old to get a Harley rather than a Honda – but he would make the final decision.
At the same time, I think we should show our parents a level of respect that goes on for life. No matter what their mom did to YOU in your marriage, there is no denying she is their mom. That respect does not mean having her over for holidays or visiting weekly, but it might mean going over and help her with changing a flat tire and being civil.
My suggestion to you is this:
As you already have then make it very clear to your ex that her relationship with her son’s is NOT your issue, other than how it impacts them.
As you already have been – be upfront to your sons about why you divorced. If you can – do so in a non-judgmental way, sort of like you are narrating what happened.
NEVER talk disrespectfully about their mom.
Make it very clear to them that you have no expectations of them taking sides. They never have to choose between you or their mom. You can take examples such as if they graduate, marry or whatever you will never make it about them choosing if they invite mom or dad.
Suggest they aren’t overtly judgmental to other people. That it’s OK if they feel negative towards their mom, but chances are that if their whole life is evaluated, she has done more positive than negative. It’s OK to be angry – but work towards acceptance of what took place.
IMHO the "end-point" (as if there ever is one...) for your recovery isn’t where you get revenge or can completely disassociate from your wife. It’s rather where she no longer matters from an emotional POV for you. It’s where you can maybe attend a son’s wedding and not be bothered that she’s there too, maybe even with her newest boyfriend or whatever.
"If, therefore, any be unhappy, let him remember that he is unhappy by reason of himself alone." Epictetus