The following is the the long-awaited followup to the OP's previous anonymous post
Good afternoon!
Had our last time fun because why not and confronted her right after. She broke down explaining everything (matched what the others said) without questioning sources or proof. Turns out she apologized to the guy a bunch of times too (don't ask) because of what she did. At least she knows she fucked up. I told her I wouldn't be able to trust her again and whatnot and she said she wouldn't forgive someone like herself either.
Okay, good, no complications... She thanked me for taking it well and we said our goodbyes, goodlucks, etc. and that's it

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I believe I made the right choice waiting until today. I probably would've been more rash and she would've been more of a hassle, and something like this is probably better resolved in person anyway. Plus I had time to get over it to make everything easier for myself.
I appreciated everyone's input, even just the memes

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Thanks!