Don't feel guilty about distancing yourself from her. What is your other choice? Continue to be abused and allow your family to be as well? I think you did a very smart and healthy thing.
And refuse outright to get into discussion with anyone about seeing your mother. If they want to stew in their own drama with her stirring the pot at the center of it all then so be it, but make it crystal clear that discussing her with you is not welcome. If you want, explain why one last time, and if you feel you have explained enough then don't. If someone won't listen then hang up, leave the room or house you are at, or ask them to leave if at your home everytime they disrespect your wishes not to talk about it after you told them nicely.
If your mom is trying to manipulate your son/s and they are of age where you can't stop them from calling her you can at least suggest that they don't call.If they don't want to hear any of that then they are not to bring the matter of "her" up with you whatsoever.
If you ever find out, substantiated by a medical professional, that your mother is life and death ill then you can decide what to do then.It still doesn't mean you have to be back in her life though.You might just want to see her one last time, a few times or you might not at all.
Its sad in one way because these people are sick but you can't let them drag you down and destroy you. You have to look out for yourself and especially for your family.
I say-- congratulations to you. The best path is most often not the easiest.