How do you treat a narcissist soon to be ex?

My wife said she loved me to death and that she would die if I ever left her. We had a big argument 4 weeks ago….she left me. She then tried to trash me to the neighbors and trashed me to her family like it was all my fault. The woman had an abortion before she left, has been driving around on a expired license with her daughter and drinks like a fish. Nobody knew this and she said her family would be horrified if they knew. I kept it in confidence until she left me and decided to trash me. They say the best thing to do for a narcissist is to expose them. They are little kids and nobody has ever exposed their flaws. On the outside they appear like saviors and pillars of the community. She verbally abused me like no one else I’ve ever been with and then left and played the victim after she verbally abused my 9 year old son. I’m sure her father never stood up for her in front of her verbally abusive mother. I did stand up for my son. The cycle stops at me and I don’t think she could take that I was telling her she was out of line so she left (a narcissistic injury to her ego). She’s furious and I did love her but I realized she’s a spoiled brat and the only way to help her is to expose her and for her to own up to her behavior. From the love of my life (her words) I haven’t heard from her in 3 weeks. How do I treat a narcissist like this?