Any advice is appreciated (long post)

I've been having some family issues for a while, it's a pretty long story but ill try to shorten it a bit. Please don't criticize because it's very hard for me to finally say this.

So a while back my mom cheated on my dad and after I found out I became obsessed with "spying" on her. On 3 different occasions she cheated on my dad again by talking to guys on the Internet, and using her web cam. My dad (a truck driver, sometimes gone for days at a time) kept giving her chance after chance until the deal breaker happened. I came home to her, and some random dude she'd been talking to online, we'll call him greg. My dad kicked her out that night.

After that I refused to communicate with her. She moved in with Greg and played the victim. She talked shit about my entire family including me because of what we did, everyone else accepted Greg into the family and pretended I didn't exist.

Fast forward a couple months, I came around to the idea of meeting my mom for a coffee to straighten things out, we slowly started to rebuild the relationship. Lie after lie from my mom about every thing I would ever ask her. She told me he wasn't a very nice man,that he would yell, throw things at her, etc. She refused to leave him and I couldn't come around to the idea of Greg being in my life so I kept my distance. Greg hated me as much as I hated him so it wasn't a good idea to be around each other. One day I got a call from my grand mother. My mom's in the hospital because "she went there saying she was going to end her life". Of course I went, got yelled at by Greg for being the reason my mom wanted to kill herself, then tried to help my mom. I stuck by her in fear that she would kill herself and it'd be my fault. I lost my best friend to suicide when I was 14 and I couldn't imagine it being my mom next.

Couple months later, mom tells me he's cheating on her and gave me a link to his pof profile. Guess what? He's a bisexual cross dresser, and my mom watches him have sex with other men. Don't think it's considered cheating if she approves. Greg and I start arguing through text, my mom takes his side, I'm the spoiled daughter that caused all of this. Bye mom.

Couple months later mom texts me saying she's feeling depressed. I feel bad and try to help, we try to rebuild relationship, etc. Then she gets into a car accident. I didn't care what my mom did in the past, didn't care about Greg, didn't care about anything, I just wanted to be with my mom and make sure she's okay.

This is where our relationship got better then ever. We were best friends. I spent a lot of time at her apartment because she moved out of gregs house. She said she broke up with Greg all was awesome! I had my mom back, I was happy. I even tried to get my dad to take her back. Then Greg starts coming around again. Greg doesn't like that I'm at mom's all the time, and I don't give a fuck about what Greg thinks so I stay.

In one hour my happiness was gone. My anxiety was through the roof, I wanted to die. I lost my mom again. She had to get minor surgery and I held her phone for her. Greg was texting her so I went through and read some messages. My mom hated that I spent so much time there, whenever I would go home she would say "wow she finally left" and other things talking shit about me and my dad, telling Greg the truth (opposite from all the lies she had been telling me). She'd been using me for information on my dad to get money.

The worst part? Her and Greg would break up almost every day. Greg cheated on her with his high school girlfriend and my mom turned back into a psycho bitch. They would break up and she would tell him she's going to kill herself and that "she hopes he has fun telling her mom why she's dead".

Now we're here. My mom still doesn't know i know and it's eating me inside. I cry whenever I think about her, I have constant anxiety. I fear that she will kill herself without me. She texts me often asking to hang out and I can't help but cringe and feel bad at the same time. since she doesn't know why I'm avoiding her, it's hard to think of an excuse. She posts things on Facebook about feeling alone and depressed. The reason I'm posting this is because I don't know what to do. Should I tell her I know? Should I cut her out of my life? I'm lost.

I'm sorry for the long post, even if this gets buried and no one replies it still feels good to get it out.