Discussing monster in law with my child

My mother in law is a narcissist. She is abusive and so (without judgement please), we've decided to not have her in our lives. It's impossible to make things work with someone who does not respect us, our boundaries, and even uses our kid against us in phrases like, "He isn't going to grow up good without me in his life." For one, my child is thriving, has a lot of people who love him and he knows it. They don't bring this negative energy into our lives one bit.