I know everyone says breakup and dump her but you may be at fault, somewhat, for this situation developing. I am not saying you should feel guilty and let her do what she wants, but learn from your mistakes so you don't repeat them in the future. It is hard to throw away a six year relationship and if there is hope you can save this, then hear me out.

You need a little more time to process this and figure out where you went wrong. Did you emotionally distance yourself from her, play too many video games or work too much? That shit happens too and we tell the girls to dump such loser boyfriends so its possible. Or did you love her too much, spoiling her too much to the point she is taking you for granted, being unappreciative of having a house together at 25. Is she very smart? Most people would realizing that having a crush on an 18 yr old is not a smart thing and the fact she has gone so far to emotionally cheat. . is she worth fighting for? Your kids are going to be dumber do to her genetics or poor rearing ability.

You know these answers and more, you gotta ask yourself and figure out what the real story is. Then you gotta decide if you want to work on saving this relationship. The house and money seems like a big deal to you but honestly, its not nearly as emotionally painful as wasting years with a woman who doesnt love you and would throw you away for a 18 yr old child. I know plenty of adults who would happily trade money to be able to change one stupid decision they did as a kid that wasted years, even decades of their lives. the house, while important. . is not the main issue.

Is this woman worth fighting for, or is she a fool that does not value you properly?