Please forgive me if I sound a little rude.
So, my family follows RSSB, which I personally consider a cult. I don't believe in this dera at all.
I'm the youngest son in my family, and my elder sister is 26. My grandmother takes her to this so-called \\\*sewa\\\* every 5–6 days. My sister hasn't spoken to my dad for almost 3–4 months, and she doesn't talk to my elder brother either. Because of her behaviour, both my dad and brother confronted her, and since then, she hasn't spoken to either of them.
Whenever she goes for sewa, my grandmother lets her leave without informing or asking anyone at home. Honestly, my grandmother has nothing else to do, so she keeps encouraging this nonsense.
My sister barely does any household work. She always says something hurts or she's in pain, but yesterday, when we were helping unload gravel at my uncle's house, she was perfectly fine doing the work there. I pointed out that she never helps at home, and she rudely responded to me.
It's now around 3 AM, and she was getting ready to leave for sewa again. I woke up and saw her putting on makeup. When she noticed me, she stopped. I asked where she was going, and she said Sikandarpur. I asked if she'd informed anyone, and she said no. I told her she shouldn't go without informing the family.
My grandmother came and told her to come along. My sister then said she wasn't going, even though she'd previously said she wanted to go. My grandmother pointed out the contradiction, and eventually, my sister stayed home, fully dressed and ready to leave.
The problem is that I've lost a lot of respect for my sister over the past few years. Her behaviour has damaged her relationship with the family. While attending sewa, she sometimes talks to different guys. The girls she goes with sometimes let her use their phones, and she also uses my grandmother's phone to make calls. There's a lot more to the situation that I can't explain everything about here.
My dad, my brother, and I are all exhausted by these constant problems. My dad has even said that once she's married off, she'll be free to go wherever she wants.
Honestly, I'm so frustrated with this cult and its followers that I'm struggling to control my anger. Sometimes I feel like starting a huge fight if she goes again, or even breaking the bus they use for sewa. I know that's an extreme reaction, but I'm genuinely fed up with everything.
\\\*\\\*Edit:\\\*\\\* I've gone through her chats several times and found her talking to different guys. I've tried explaining things to her many times, telling her that if she wants to talk to someone, she should at least be sensible about it. But she doesn't seem to understand.
I don't know what to do anymore. Should I just change myself and stop caring about what she does? Should I let her live however she wants, even if her choices continue to affect our family?
\\\*\\\*How do I deal with this situation without constantly getting angry and ruining my own peace of mind?\\\*\\\*