The other thing you might mention to your GF, Brandon, is that the older the daughter gets, the harder it will be to let go of those other guys...the more she will remember them. She is only 4 years old. I would get the ball rolling on her seeing him less and less now, rather than later.
Like I said, it isn't good to rip the kid away from the guy/guys, but a thought out plan of distancing the girl from them is a good idea.
Good luck.