narcissistic friends

Selina
So I have been friends with this woman since high school-- we weren't close in high school, went to the same college during freshman year; she transferred and we remained in touch. We didn't become close until a couple of years after graduating college. We're both 34 and have known each other since we were 16. 
I had my first baby in September of 2016 and was diagnosed as having PPD in January; I'm currently seeing a therapist for it. Because of my PPD, I have scaled back our friendship significantly because a lot of the things she does mainly her behavior contributes to my "episodes."
She too has her own mental health issues, is on a lot of difffent meds and is seeing a therapist. Long story short, my therapist as well as several of our close friends all believe she is a narcissist. It has gotten to the point where my therapist doesn't want me to be friends with her anymore because he feels she is contributing to my own issues. He says narcissists will "suck the life out of you" which is what it feels like. 
She has done so many things that I won't even get into but no matter what the situation is, she will 1) make it about herself 2) never own up to her own actions 3) gas light you and 4) you ALWAYS end up apologizing to her when she was clearly in the wrong.
Tonight was the last straw for me because she sent a message once again trying to gas light me and make me feel bad. She also said she isn't going to dinner anymore on Friday which I feel like to me is her wanting me to beg her to come.
I just can't anymore!
If anyone has ever dealt with a narcissist friend, I would like some advice!