Narcissistic mother

Hello- I’ve been going to see a therapist this Summer to get advice and help around my relationship with my mother. My relationship with her brings betrayal, dishonestly, rude texts and lashing out at me. The therapist had me read the same book on Boundaries that you recommend and she helped me see that my life is so much better without my mom in it. I just wanted to heat your perspective on setting the boundary of not having a relationship with someone?