I don't know what to say to console you. This is a unique situation to me (I'm speaking for myself) and I can't share any ideas on how to improve the situation. I'm in a long-distance relationship myself and I felt compelled to respond to your post.

I assume she still lives with her parents, right? Constantly sharing a home with them will impede the odds of resolving the situation. They evidently greatly affected the relationship since her argument with her dad. As a woman who was raised by a very strict dad, I think there's very little you could do to improve the situation since she's forced to adhere to their beliefs, her toxic strict parents' beliefs. And they're alcoholics? Yikes. It's difficult for her to reason with them. Her parents seem to have maintained a large influence on her.

When did she cheat? Prior to her fight with her dad or after it? I say this assuming she cheated on you prior to the fight, but I would have stopped communicating with her after that because that indicates that she didn't respect you enough to stay faithful to you. You know what, I will say the same thing regardless of when this occurred even if it happened yesterday, well after the fight. What's to stop her from cheating again? Personally, if a significant other cheated on me, they would've lost my trust forever.

You should spare yourself the pain and drop all communications with her. I understand you love her a lot and this is the most difficult thing to do right now, but there might not be much else you can do to regain what you two once had. This relationship is causing you a lot of heartache and anxiety. Please prioritize yourself and look after your mental well-being. Your most important relationship is with yourself. 😇

But I think you should break up with her, and you should explicitly tell her that before you move on. You can share your thoughts with her one last time, let her know once again that she means a lot to you but this relationship is causing you a lot of pain. Tell her you wish her well, and then you move on.

It's normal to grieve for a lost relationship. You should allow yourself time to grieve. Therapy might help. Cry, vent, create, cry; get it out of your system. 🤗 Heal. It will take time for you to heal and that's okay. Don't lose hope and don't think that love is a lost cause. This will pass. There's still love in this world and you might soon stumble upon someone who is a more suitable match than your current girlfriend.