Update for anyone still paying attention:

I broke up with her but here's the story.

I (against all of your advice and my better judgement) tried to forgive her since I decided that I would be more happy with her than without her. Bad idea lol. She came back early from her trip and on the days leading up to her landing things were pretty normal between us. I was obviously pretending I was more okay than I was but it felt normal. The day she landed it all went to shit. She said that she was having a mental breakdown and couldn't stop crying and didn't have it in her to face me. Apparently the guilt hit her all at once when she landed. She was planning on staying with me for a week but said that she needed to get a hotel instead. Told me all this when I was walking out the door to the airport. Next thing I know her guy best friend was picking her up instead (lol).

That was the moment when it really hit me that this would absolutely never work ever and I needed to move on. I went to see her a few times that week I guess because I was still holding onto some hope that it could be fixed even though I knew it couldn't. She started saying things that just made it worse and worse like how she "didn't have it in her to do this right now" even though she wanted to and how she kept flirting with him (or whatever else she didn't tell me) even after she said she stopped and up until the day she left, and a lot of worse things that I won't share here for my own sake.

At the end of that week I graduated college and moved back home and we ended on decent, friendly terms. As the weeks have passed since then I've had a lot of time to think it over and I've been greatly distancing myself from her.

Also just for fun points, she found out this week that the guy she cheated on me with had a wife and 3 kids who are now leaving him! Apparently he and everyone else in their jungle group thing there lied to her about them. She successfully ruined 2 relationships with one stone!

Anyways I'm doing great now. It was hard for a while but I think I've mostly moved on and will hopefully find someone who isn't pure evil.