It was a shitty high school drama thing but it had an impact because up until that point I had been a totally trusting, people are inherently good see the best in everyone type of person.
Like a lot of high school drama it had to do with a totally cliche teen drama backstory. There was this guy in my class we'll call him "Zane" and well he was the 'bad boy' constantly in the head of schools's office (thought that wasn't hard to do - long story for another time). I was the totally sheltered shy girl that wasn't unpopular but wasn't going to make head cheerleader or anything. He and I were in the same friend circle group in school, there were about 5/7 of us that were all really close friends. Zane and I start to date (or what high school teenagers qualify as dating) little glances in the hall, hand holding, spending 'tutorial' time together after class. Well James gets to the point where he's not interested in anything serious. We break up, go back to being friends (classic me as Mosbey him as Robin friendship after relationship dynamic).
Now enter this other guy, we will call him "Andrew", well Andrew was a year older (so sophisticated in a high school teen mind). He was a total nerd though, had a few friends but not many. A little odd, but ultimately incredibly sweet. He likes me and asks me to Halloween dance, and even though I said yes wants to ask permission from my mom to take me type of nice guy. We go to dinners/movies etc.
Now enter the betrayal. The girl I thought was my best friend we will call her Cheryl passes me a note in history asking if I still have feelings for Zane. He is the Robin to my Mosbey so of course I do and thinking Cheryl is my friend that I can confide in I tell her the truth. I do. But being a dumb freshman I take it a step further and say I would much rather be with Zane than Andrew if that were a possibility. Well later in the day Andrew pulls me aside and says we need to talk. And to my absolute horror I see him holding the note that Cheryl and I were passing back and forth in history. Needless to say Andrew was hurt (100% rightfully so) and we broke up. He told me that Cheryl had given him the note when I asked him how he got it. Cheryl the girl who I thought was my bestest through thick and thin friend had just handed it over.
Again like I said no where near I'm sure some peoples betrayals that ruined friendship but because it was really my first taste of it and cost me a great nice guy high school boyfriend it still has a sting to it.
TL;DR High school drama bullshit. I liked bad boy, dated bad boy, got dumped by bad boy, started dating nice guy, possibility of being with bad boy opened up again and I jumped at it, girl I thought was my bestest through thick and thin friend went and told nice guy BF what I said in confidence and ruined my relationship (which being a bitchy 14 year old I totally deserved but still wasn't her place to share a private conversation like that).