I need to vent about this…

My mom and I both have bpd, but hers is much more severe. She’s not in therapy and has substance abuse issues along with hers. 

She single handedly destroyed my entire childhood. My only good memories of my mom are admiring how physically beautiful she was. I actually remember thinking how she looked like a princess. I was just always in complete awe of her looks.
Aside from that though there wasn’t anything else. 

I was the scapegoat child. My mom abused me emotionally, psychologically, and physically. She also used me to vent to about all her adult problems. I was so terrified that within seconds she could switch from venting to me to rage that I had to be very careful with my responses and support. I carried a lot of anxiety from her venting sessions too, because I always though my dad would leave us, because he cheated. I also always thought we were about to be homeless (from money issues) or someone would die (from health issues). 

To this day I have a scar on my lip as a daily reminder of her physical abuse. She slammed a door in my face when I was in 3rd grade and locked me up. She didn’t believe me when I told her I was bleeding and left me like that for hours without any first aid. Of course afterwards she didn’t take me to the doctor or even ice my face. That’s the only mark she actually left, but the abuse was consistent.

She regularly tore me apart about my looks. I still struggle with body image issues from that from my weight to what my face looks like. She also invalidated every single feeling I had from sadness, to anger, to happiness. None of my feelings were acceptable, so I had to be as natural as possible at all times to avoid her wrath about me not having the “right” to feel a certain way. 

Currently I have minimal contact with her. I had confronted her about the abuse and she denied it. Once I brought up very specific details she blamed me. She told me she did her best, but I was a difficult child since I was born. She said since she first laid eyes on me she saw I had a devil in me and she had to constantly put in the effort to correct me, so I could be the person that I am now, instead of someone horrible.

I only have minimal contact for my dad. Anyhow my dad is ill, and my mom who has two masters degree, but chose to get a low basic paying job outside her field is trying to use me as a back up plan. She wants me to take her in in her old age. I know this is common with bpd, but regardless it makes my blood boil. Like how dare she? After everything she did, how dare she think she can come live with me and ruin my three children? She actually regularly asks if I told my partner anything a bad about her, because she’s afraid he’ll say no when the time comes. I don’t know how to even begin to tell her no and how I really feel, because I know she’ll start drinking and take it out on my sick dad.