Advice? Stay out of it. Sounds like she dealt with it as best she could, and not her fault. She (says) she made things clear, now she just needs to avoid him completely, and not talk to him. Don't respond to texts, etc. And if he pulls that shit at work, or goes for her again, you're a little more justified. Basically, he took a shot and screwed up. It's what he does NOW that matters.
Not defending him, but who's never taken a shot at someone that had a boyfriend/girlfriend? Not talking about some woman with a husband and 3 kids, but hey, it happens. Attraction is funny like that, and most people tend to think highly of themselves, so why wouldn't you think you could be better for her than that 'other' guy? Once you get shut down, though, gotta walk away...