MIL & SIL calling me fake, manipulative, and a backstabber after I tried to set respectful boundaries

Hi everyone,
I was living with my partner and his mother in a divided home situation for 3 months (separate floors but shared entrance), which was very difficult. His mother has a very rigid, cold, and controlling personality. She was extremely critical of me, spoke to me like a child and dismissed my feelings. In the past, I’ve made efforts to form a relationship with her, but I was met with hostility, outbursts in front of guests, and no acknowledgment or apology afterwards. She created weird theories that I was trying to kick her out of the house, that I hate her and that I was giving dirty looks etc. Despite this, I always tried to be polite and neutral, being the bigger person even when I was hurt.

Eventually, I took some emotional distance to protect my peace. I never lashed out or bad-mouthed her to others. I spoke to my partner calmly and respectfully, and eventually wrote a message directly to his mother to set boundaries. I said that I felt disrespected, explained my perspective clearly, and asked that we engage with mutual respect if we are to coexist. I also emphasized that this situation was impacting her son emotionally, and that it wasn’t okay.

One specific situation that seemed to tip everything over: I had placed some of my belongings (clothes neatly stored on shelves and in boxes) near the entrance area which was to become our build in closet (the renovation wasn’t complete). His mother didn’t like the way it looked and moved my things without telling me. I left a message kindly requesting that next time she communicate with me directly about it—and in response, I was blocked. That’s the kind of dynamic I’ve been dealing with.

The final straw was being labelled fake, manipulative, and a backstabber—both by her and my partner’s sister, who I’ve never even had a negative exchange with. It’s as if, once I stopped being compliant and silent, I became the enemy.

What hurts the most is not their disapproval, but that they have built an entire story about who I am based on their discomfort with someone who won’t fully conform. My partner is somewhat supportive and acknowledged the dynamic, but I still can’t talk to him too much about it because he gets easily triggered or shuts down.

In the past when I was simply a guest at the house and didn’t have any conflict, I was praised for being such a good influence on his son. But now apparently I’ve been manipulating him since he doesn’t call as much as he used to (wonder why lol)

Has anyone else experienced this kind of unfair character assassination for simply trying to exist peacefully with boundaries? How did you emotionally process being misjudged so severely? I’m currently planning to save up for my own apartment and focusing on my goals, but the sting of being misunderstood like this still lingers.

Thank you so much for reading.

TLDR:
Tried to set respectful boundaries with emotionally controlling MIL after many difficult interactions. After she moved my things without permission, I left a kind note asking for communication—and was blocked. Later, I sent a message explaining my feelings and asking for mutual respect. MIL and SIL responded by calling me manipulative, fake, and a backstabber. Struggling to process how deeply they’ve misjudged me, even though I know their version of me isn’t true.