I seriously hope our protagonist finds someone else that is right for her, because she seriously deserves better than this infuriating cheating bitch.
If she was actually feeling guilt she wouldn't have gotten in the damn car with her. Guilt my ass.
Her friend did a shit job of being a friend at the bar, i'm sorry but even if she is your friend and coworker in the band you have to call out shit behaviour.
Cheating is not okay.