How can I stop obsessing over my mom?

I stopped talking to her over a year ago because she plays so many games with me and the rest of the family. She undermines my authority when it comes to my kids and she basically plays the victim so we feel obligated to take care of her. There are six of us kids and I'm the fifth child. She chose to live by me, which is 7 doors down from us. I let her know I wasn't going to play her games anymore and she told the other kids how aweful I am and so they all play with her and won't speak to me anymore. I have two sons, one who is 6 years old and has spent most of his life around her. I broke off that relationship when she slapped him in the face because he was being too wild. The other son who is 8 months old has never spent any time with her. She didn't acknowledge my oldest son's birthday a few days ago even though she lives a few doors down. Although not keeping in contact with her is good for me, I can't stop obsessing over her. What can I do?