I might cut off my best friend and its killing me

So, yeah, iv known her 3-4 years. She was my everything. I'm alive because of her. But since we graduated, my eyes have opened up and she's changed into a person I don't even recognize.

We were so close, she was a sister that came in when I lost one by blood. We were side by side for years. When she got to collage, she changed. 

She started drinking, cutting off people who loved her, dropped her major, cut herself off income taxes and lost financial assistance, she's hanging out with bad people, she's lying more, and much more. Lately all her lies from all the years are comeing out. She was narcissist and I fell into her trap. 

As of today, I just hit my breaking point. Her and another friend are teaming up on me. Even though I love her to death, I think I might have to let her go for my own wellbeing. Iv never been good at that. We used to be inseparable. Now, I don't even know her anymore, I don't know what is lies and what's not.

This hurts me horribly. Finding out that she was only there for me when it benefits her or when she's jealous killed me. For example, when I went through an abusive relationship, she was there on because she was jealous of the attention.

I'm crying writing this. There is so much more to this too that I don't feel comfortable sharing. In the next few days, imma have to decide whether to cut it off before I end up dead because of the bad mental health she puts me in. I'm honestly hurt horribly and betrayed.  

I'm not asking for sympathy, I'm just venting. But let this be a lesson that even though you love someone, it doesn't mean they love you (platonic and romantic)