@mike6500,
If she was your first love, you hers then it's call "first bonding" in which case as you now say love/ lovers, it suggests that.
Marriage is a piece of paper, commitment of 4 years and a baby, living together might as well be a marriage.
I don't think you should force her to do anything. You say you were a mug the first time, you can "suggest" and ascertain from there whether you would have been a mug the second time or not.
Maybe she has to work out her in-differences with this guy, "on her own" without interferance from another guy who perhaps was her first love...
If it's meant to be it will be, later down the track. But, I think your presence is possibly confusing the issue.
Suggest, if that doesn't come to fruition walk. You could possibly be assisting her emotionally where otherwise, this boyfriend is not providing her with same.
Who know unless you walk and stay away...