BIL has confided that a lot of their fights center around me and making him admit what a horrible person I am. Dont get me wrong, they have an incredibly toxic and abusive (physically and emotionally) relationship outside of me as well.
Hey aspiretogrow, great name

When you're in the fray it's very tough to not be impacted.
Disordered people seem to prefer drama and chaos to feeling ignored or empty. Feeling nothing but her own pain is likely intolerable so she looks for something else to focus on that's less painful (to her). Maybe she perceives you interact with H and BIL effortlessly which triggers jealousy. Doesn't matter, really, but there's a good chance the original issue begins with her and her relationships with BIL and H. You are simply a catalyst for a drama starring her. Perhaps she doesn't want to share their attention, and/or she uses these fits of anger to keep BIL focused on her.
A book that really helped me was
In Sheep's Clothing: Understanding and Dealing with Manipulative People. It wasn't an option for me to avoid my stepdaughter and like you, I had some prior trauma I was willing to address. That book helped me realize SD27 is different than me in ways that will not change. She's in my life and that also isn't going to change. I wanted to learn how to neutralize the ways she was "winning," since that is much of what drives SD27. Disordered, aggressive people struggle with genuine intimacy but want it, and since they can't generate it on their own, they want to "win" things to approximate what a loving or respectful relationship looks like. It's a hollow effort. Unfortunately, whether we like it or not, we're often losing a battle we didn't realize we were in.
The other thing I would read is
Bowen's family systems theory especially about
triangles and
differentiation of self. This thing with SIL is likely more about BIL and H's family and how they do conflict. If you're a reader and want really understand drama triangles, most of Harriet Lerner's books are about that concept and how to not "over-function" when there are codependent traits and chronic family dramas. Karpman drama triangle is the Cliff's notes but I needed more in-depth help when SD27 lived with us and Lerner's books really helped the concepts land for me.
I'm curious how your H supports you during the times you have to see SIL? Do you feel he tries to protect you? Or does he seem to sort of go into survival mode on his own?
When stuff with SD27 was at its peak worst, I worked with my therapist to take inventory of moves my stepdaughter did to generate a one-up or one-down position. Then we looked at ways my H's responses did or did not enable her to perpetuate bad behaviors. We talked about whether he was preventing me from having boundaries, and if so, what I would do to make sure I had control over my boundaries so I didn't give that power away.
For you, it could be telling BIL (if he keeps telling you what SIL says) --Hey, I got the picture. That's enough. I'm sorry you get an earful. It sounds rough. Please stop sharing.
With H it might be the same, plus maybe something like how long you plan to spend in SIL's company. Is there room for negotiating how much you participate? Are these gatherings just the four of you or are other people present?
I had something that helped me stay flexible in my relationship with SD27. I envisioned a cup and my sole job was to fill it or keep it full. If I woke up tired or didn't feel well or had a busy schedule that generated anxiety, I focused on filling my cup. When it came to SD27, I gave nothing unless my cup was full. If you find yourself heading to these 2x monthly events and do not feel your cup is full, what consequences are there for tapping out? Not as a long-term solution so much as a signal to yourself that your needs come first. Schedule a massage instead or go out with people you feel safe with or whatever fills you.
Don't beat yourself up for caring about how this impacts you. She's an aggressive bully who is targeting you. Your nervous system is doing exactly what it should do. You're still gathering the skills that will require practice and repetition before you see fruits of your labor and there is some earlier trauma that wants and needs processing. I neutralized SD27's aggression and my nervous system still gets triggered. She used my bathroom during her last visit and I about had a heart attack. It took a while to return to baseline but I understood why my reaction was both reasonable and off the charts.
In my situation, it was when I realized I was on my own --my husband was in the grip of his own issues in dealing with her -- that things started to swing in my direction. I began to compartmentalize this aspect of our relationship and set boundaries with him so I could have real boundaries with her, if that makes sense.
If you do opt to limit your time at these gatherings, if it were me I would really focus on making something fulfilling and wonderful happen when you opt out. When SD27 lived with us, and actually even now when we plan gatherings, I socially engineer as much as I can so that my needs are front and center.
Also, don't discount the impact of SIL icing you out. It's a way to make you feel erased, which for some people is worse than being yelled at. Have you talked through this with your T?
My stepdaughter does this to me as well. If my cup is full, I focus on keeping it full so she has a harder time draining it. I think this is why it's so important to heal old injuries because doing so makes it easier to counter this kind of battle. I also put more effort into strengthening my relationships with other family members and now have H's full respect when it comes to SD27 because I neutralized her behaviors toward me without creating any long-term chronic conflict.
It's still really hard even though she doesn't live with us anymore. The truth is I don't like her and have to accept I'll never trust her. But my motto is that we don't have to all like each other, we just have to make it work. pwBPD traits cannot make it work so you'll have to be the emotional leader. That is not anything like being codependent or being a caretaker, although if you've healed some of those tendencies they can come in handy. As long as you understand the significance or taking care of
you.
