“A couple years ago she held a knife to her chest because she was angry at her own mum for some reason.. she asked me and my sister if she should kill herself. It was very scary and still affects me to this day. My sister and I were frozen. She eventually put the knife in the draw and went to her bedroom.”

Your mom has done several abusive things you already mentioned, but let’s just look at this one for now: First or all, doing that was her being over the top dramatic. I doubt she’d have really stabbed herself. So she did that to get a rise out of your sister and you. She traumatized you both and she only did that for effect. That’s abuse.

And seeing her do those kind of behaviors taught you to do similarly unhealthy ones yourself. If you’ve been diagnosed with borderline traits (and so have I just FYI), you probably are feeling this unhealthy way because you subconsciously learned it from watching her.

I’ve spent much self reflection about my mother and myself and the symbiotic relationship between mental illness or just learned behaviors.

This may be a good place for you to begin with a therapist to discuss. I hope you can get a good one.