This is my first time posting on reddit but, this situation is so bizarre that I need outside perspective. Apologies in advance for the long post and all names used are fake. I (24F) live with my mom and niece (Lily). My brother (29M), I'll call him Jake, and my SIL (30F) moved in last year due to financial circumstances.

Their relationship was always very unstable and toxic. When they had first moved in, they promised that their relationship would not affect us. But, within a month, their arguments started. It was like living with a ticking time bomb. When my SIL is angry, she curses and throws things at Jake. Jake will tell her hurtful and demeaning things like "I hate you" and so on. Mom and I have learned the hard way not to get involved because when we do, in a matter of days, Jake and SIL will be back together like nothing happened and we would be scolded for getting involved or be treated like strangers for a few days. If we tell Jake that he's wrong, he'll try to understand but, if I say the same to SIL, she shuts down and stops listening to you.This went on repeatedly for the entirety of 2024. In December, with the financial help of my dad, Jake and SIL opened a cafe together. This caused new tension because the business did not do well for the first month.

In January 2025, another argument ensued in which I got involved and said some harsh things to SIL. She packed her things and left to go back to her hometown that day. Feeling guilty for the things I had said, I reached out to her the next day and apologised. She blocked me and within a couple days, she moved back in with us, but, proceeded to ignore me - so, I did the same. In March, they had another argument at midnight which escalated to a physical fight. Jake broke SIL's phone making her angry so, she slapped him and tried to hurt him with objects around her. She reached for a pair of scissors which made Jake put her in a chokehold. He then threw her outside. SIL called the police and so, Jake was arrested. After hearing both sides of the story, the sergeant counseled both of them and they agreed to work things out again.

However, SIL had made both a Facebook and TikTok post saying that Jake abused her while mom and I stood by and did nothing to help. She moved in with my grandmother afterwards, because she has nowhere else to go. My grandmother forced SIL to apologize to us for the way things happened but, the apology was so forced and she didn't apologize for anything specific. So, I simply listened and didn't say anything. Later, Jake told us that SIL expected us to also apologize and for things to go back to normal.

Weeks went by, until on Sunday, mom and I were at my grandma's house when SIL came back for something. She said "good afternoon" to which my mom replied loudly enough for her to hear but I responded in a low tone. Yesterday, I received a text from her threatening me that I should not do anything for her child and that I will learn the difference from when she's being bad versus when she's being nice. Jake said that, she's angry that I did not say "good afternoon" to her and that we betrayed her by not helping her the night of the physical fight. I should also note, my mom and I raise their child. I take care of all of Lily's educational needs and anything else I can help her with (think of basic things a mother should do for their child). So, should I have handled that differently? Am I the asshole?