My 27-year-old sister and my 50-year-old mom had a disagreement right before my trip to Thailand.

Firstly, I apologize for any grammatical errors; English is not my first language. To begin, I'm a 21-year-old man, and about a month ago, my 56-year-old father asked me to join him in Thailand. I seized the opportunity to travel, as it has always been a dream of mine. However, this is my first time flying alone, especially on a long 15-hour flight, and I tend to be quite anxious. To help me cope, my 50-year-old mother organized a dinner with my sister, who is 27, and me, followed by a trip to the airport together the next day. We went to a lovely Greek restaurant, and when we got home, I wanted to play one last game with my friends. During the game, my sister and mother ended up arguing. They have a turbulent relationship, as my sister had a troubled adolescence; she ran away, experimented with drugs, stole from my mom, and a lot more. After the game, I went to see what was happening, and they were screaming at each other. I asked them to stop, but they didn’t listen. My sister became very angry and started hurling insults at my mom, calling her "the worst mother." I had only asked them to calm down, but then she directed her anger at me too. My mother and I are really close; my sister was absent for much of my childhood. My sister accused my mom of always protecting me, despite her own absence. I noticed that my sister had dilated pupils, which made me think she might have been using something, and the alcohol certainly didn’t help (I don't drink, but they do). Things escalated when my sister became physical, slapping my mom, who then just pushed her away. I stepped in to intervene, and while my sister calmed down somewhat, she continued to hurl insults before storming out. I can't shake the feeling that this is my fault. I don’t understand how things got so out of control, especially since we had been working to mend our relationships lately. My sister and I had been talking almost every day since my mom's struggles with depression, and now I'm leaving with the guilt of having created this situation when I only wanted to enjoy a nice evening with my family. I have a flight tomorrow, and I'm really seeking some advice. Thank you for taking the time to read this. I hope it makes sense because I don’t have anyone else to talk to.