>>33279116 (OP)She did nothing wrong.
It might ordinarily be weird to have dinner alone with another man, but these are special circumstances, so the weirdness is negated.
It would ordinarily be suspicious af to have dinner alone with a man without telling your boyfriend, but she DID tell you, so the suspicion is negated.
It would ordinarily be shitty behaviour to have dinner alone with another man despite knowing it makes your boyfriend uncomfortable, but she gave you the opportunity to express your discontent and you said nothing.
It's fine if you're uncomfortable with this sort of thing, and if it comes up again, it's perfectly reasonable for you to let her know that it makes you uncomfortable (you should have said this from the beginning, but that's neither here nor there). But there's no reason to say her behaviour was 'seriously messed up'. You've made up all this insecure bullshit in your own head, and let your friends gaslight you into thinking you're being cheated on. Like a bloody woman.