Toxic relationship with sister

Hey there!
So I’ve really been practicing the model with my family relationships. In some of the healthier relationships it has worked wonders! And I’m still struggling with it in other relationships. I’m being patient with myself as I’m recognizing that these are patterns that have been here for a long time and were caused from trauma, and will take time to rewire. I’m also employing somatic experiencing therapy to help out (which is amazing in combination with the model!) because I have learned that a lot of my responses are programmed into my nervous system as well and not just my mind.

I grew up in an abusive household and have had to do a lot of work to undo the patterns that were engrained into me. I am doing my best to live a healthy life, have healthier relationships, communicate with love and kindness, and process my feelings in a healthy way so that I don’t perpetuate the toxic patterns of my family.

The part that I’m struggling with is that my sister is still very much entrenched in those patterns and is pretty frequently attacking others – especially me. I have done my models on her which look something like this:

C – Sister
T – She’s being crazy and attacking me, I don’t deserve this treatment
F – Angry, resentful, indignant
A – Resistance, get sucked into her drama
R – Fighting, upset, stress, nervous system upset

C – Sister
T – I have a choice in how I want to think and feel about her / maybe she’s not being crazy, maybe I’m just thinking she is and I can let this thought go and give her the benefit of the doubt
F – Calm, centered, safe
A – Ignore her actions and treat her with kindness
R – More peace for me internally so long as I can keep not responding to her

And I’m still struggling here with her. 🙁

I live with my grandma, who lets my sister come stay a few nights a week temporarily. I behave kindly to my sister, am supportive of her, help her out, do nice things for her, ignore her when she’s grumpy or having attitude, do my thought work on it, give her the benefit of the doubt, and I feel like she just keeps pushing and acting worse and worse towards me until I respond, then she gets vicious and an argument ensues. Which is a pattern in my family that I have worked so hard to get out of.

This is the pattern that she continues to have:
Negative thinking towards others (me) > resentment and anger > attack and accuse > others (I) become defensive > an argument or fight ensues > attack & defense > nothing gets resolved.

The most recent example is that she created some mind drama that I’m maliciously forcing her out of my bathroom in the mornings and she is upset over it so she has a negative attitude towards me, gives me the silent treatment, sends me passive aggressive texts and proclaims how shitty her day was to my grandma because her day started shitty. When really, I just want to use my bathroom because it’s my bathroom, I go to the bathroom when I wake up, and I’m on my monthly cycle and need to access my feminine products and whatnot. I’m not even upset or annoyed at all that she uses my bathroom to get ready when she stays here, and I don’t mind asking her if I can use the bathroom when I wake up. I just want to be able to share the bathroom like normal people do. But she kept treating me worse. And I had no idea what she was upset about so I finally said to her that I didn’t understand what she was upset about and she launches into this crazy attack of how I’m so inconsiderate and rude because I “kick her out” of the bathroom when she’s getting ready, her schedule is more important, she shouldn’t have to move her stuff, I should move all of my stuff to the other bathroom, etc, etc…

And I’m not proud of myself for then engaging in the argument but I feel those primal response kick in of feeling attacked and wanting to defend myself. And I was just feeling so shocked and frustrated that she would blow something so out of proportion and not have consideration for me.

I recognize that I am having a lot of thoughts about her, but I’m stuck in the space of not knowing how else to feel and not knowing a better thought to choose. I know that I can choose to think differently of her actions, but it doesn’t feel true for me right now. I genuinely feel like her behavior is toxic and that she is someone I don’t want to even be around because I don’t want this type of behavior in my life. It feels like psychological abuse to me at this point and I wold like to get to a place where I can truly not react when she’s acting like she acts.

A huge part of me just wants to just distance myself from her because of how unhealthy it feels for me mentally and emotionally, but unfortunately she comes over so I have to deal with it for now.

At what point do I create healthy boundaries with this person by avoiding contact with her and letting her know I do not want to engage but I would like to have kind, respectful communication when she’s here vs continuing to do my own thought work to just try to stop being bothered by all of this? I want to feel resilient and not let any of it bother me, but it seems almost impossible to keep facing the same abuse over and over again without feeling something. At what point do I just say “no more” and cut the relationship off? And how do I do that when she comes to stay at our house?