My Sister Cheated on me With My Boyfriend, and i don't regret what i said to her on a text message

A few days ago, I discovered that my sister had been sleeping with my boyfriend (25M, now ex) for over a year. They were close, but I thought it was just about video games, which I don't like. It turns out they were actually planning secret dates while I was busy with work and college. I found shocking photos, videos, and messages where they compared themselves to me and talked badly about me.

First, I threw out all my ex’s stuff and insulted him, keeping only the PC I had given him. I didn't speak to my sister for a week, and she didn't reach out until yesterday. She sent a message saying it was a mistake and that I should forgive her because we're family. I considered trying to be mature, but instead, I wrote her a long, harsh message, calling her out for everything and telling her how much she envies me.

She replied with a voice message, crying and saying she’s in a bad mental state, but she’s still with him. I responded with a laughing emoji and didn’t listen to her message.

Was it low to attack her flaws? Maybe, but betraying your sister is worse, and I don’t think I should forgive her just because we’re related. I feel good after sending that message; it was a way to finally close this chapter.

By the way, I’m now looking up tutorials on how to download The Sims on the PC. I’ve always helped my sister, but this betrayal is too deep. The things I saw in those chats, especially how they mocked me, were too much. She’s dead to me, and my parents know it. I don’t care if others think I’m in the wrong; I don’t feel bad about my reaction.

The message I ended up sending her was longer than I had intended, but I trimmed out the parts that were deeply personal or outright insulting. I was raw with anger and pain at that moment, and much of what I said came from a place of hurt. For the sake of clarity, I’ve removed the overly harsh bits, but the main points remain.

"I don't want to hear any of your justifications. I trusted you wholeheartedly, especially after the falling out you had with your ex-friend group. I stood by you because I believed you were better than this. Now, I see why people keep distancing themselves from you – and maybe it's something you deserve.

What you did to me was cruel. You knew it, but you didn't care. You spent an entire year with him, acting without a shred of shame. And when I finally uncovered everything, you went silent for days, hiding instead of facing me. It’s clear that you only reached out now because Dad must have cut you off, and you're desperate for his financial support again. It’s pathetic that your concern isn’t about the betrayal but about fixing things for your own gain. I always knew you could be selfish, but this? Sleeping with my boyfriend? Have you no self-respect?

We’re sisters, yet you’ve stooped so low. I saw the messages between you two. You even went so far as to compare yourself to me, body and all. That’s twisted.

I never did anything to deserve this from you. I loved you, genuinely. But now, you’ve got what you wanted, right? He’s with you. Enjoy it while it lasts because it won’t. Eventually, you’ll be left all alone, and when that happens, don’t expect me to pick up the pieces like I used to. I’m done playing that role for you.

Stay with him if that’s what you want. The last thing I care about now is fighting for someone who will probably abandon you soon anyway. Just know this: we’re no longer sisters. If I see you in the street, I’ll walk the other way.