Deal with narcissist abuse

As per my therapist, my mom has narcissism. I have spent some time distancing myself from her to process this and to heal. I am reconciling how coaching can apply to situations with her.

For example, it is hard for me not to blame her for my lack of self confidence issues or challenges with my relationships.

Also, going forward, how do I protect myself and not keep giving her the benefit of doubt by asking how my thoughts about her or about what she says could be untrue/different?