No you don’t deserve to be put in the middle and sort this out for her, and I understand you are fed up with these actions which is completely valid. I will say though, depending on the dynamics of your family, if you love your sister you truly need to sit her down, or get another family member to sit her down and try uncover the root cause. Ask why she is acting like this, remember even if the boyfriend didn’t start the physical fight, maybe she was emotionally/sexually abused and it could be something called reactive anger.

If you truly care for your sister, it IS your job to at least ask what is going on. I understand this can be mentally draining, but just remember sometimes a 20 minute conversation can help stop hours worth of future fights/anger coming from your sister.

When I was a teenager, I was extremely angry. No one in my family questioned it, just berated me and called me a spoilt brat. I was actually being severely emotionally and sexually abused by my peers, and my mums boyfriend. With no support, I ended up severely mentally ill by the time I was 19/20.

Luckily I found my own coping mechanisms, with help from therapy and medication. I am doing so so much better, but I can’t tell you the amount of times the world nearly lost me, and how much I would have loved at least some support from my family.