<human>: Can you provide a brief rundown of the text in within 3 sentences?

Fuck.
I (23M) have never experienced such disregard, such malice. Our relationship was very new. But it seemed so fantastic. She has a history of getting a bit out of control with her drinking, and it doesnt help that she's pretty enough to get as many drinks as she wants. Earlier this week she had told me she wanted to go out with her co-worker/girl friend. This girl always told her how much better she could do, or how much of a player I was. Except, I don't know her friend at all, and I treated her like gold. She had a sedistic way of taking revenge on me for the most ridiculous reasons. She would flirt with other guys, give out her number, etc. I shouldve seen problems from miles away, but I never EVER expected what happened tonight.
 We spent last night together and it was perfect. We had plans to have a sleep over after her girls night. Last night, my now ex (F22) got drunk with her friend at a bar nearby. I wouldnt want to over step my boundaries so I went to a beer bar nearby with some friends. She called me (drunk) and wanted to meet up. I was stoked. But things took a horrifying turn. Long story short, we had a mild fight in which she implicated that I had been completely dishonest with her throughout our relationship. Which is false. I proceed to leave. Get 7 calls from her, to which I dont respond. Then I see a voicemail pop up. She left a voicemail while having sex with a random guy. I know this post is all sorts of messy, but I just don't know how to feel right now. Who would do such a thing over something so minuscule?
As far as I am concerned, shes crossed too far to come back.
<bot>: My ex made a series of poor decisions which ultimately resulted in the indefinite ending of our relationship. Shitty circumstances. Last night.