The complaining about a partner happens also with men. People vent even when they have no intention of leaving. I mean, my coworkers always complain about their wives, but it is understood that they aren't complaining seriously, just venting.

You might want to consider that women are the same. They vent about their boyfriends, but their complaints aren't always serious.

Also, sometimes the supposedly "bad" boyfriend is only considered bad by the guy who wants to replace him. I mean, how many times I've heard that a boyfriend was "bad" just by liking metal music? I also liked that music, by the way. They looked tough so they must be violent, right? Wrong.

But I agree that if you don't want to be a friend, it is better to just stay away.