For what it is worth, I have a Secondary's perspective on the situation....
Is the girlfriend paying any attention to how this guy is treating his wife? Because, really, if I saw a guy that I was dating neglecting his wife and newborn? I'd be gone so fast!
NRE or not, I'm perfectly capable of seeing that how he's treating his wife is how I would be treated once the NRE wears off. I wouldn't touch a guy who was neglecting his responsibilities at home with a ten foot pole. EWWWWW!