House - girlfriend's rights

Living in Washington you build "community property" when you acquire property while married.  If you put the land title in your name while married, it would be presumed to be community property and 50% your new wife's property.  If you put title in your name BEFORE you marry, you may be safe.  BUT, when you pay the mortgage with your "community property earnings" she will be building a community interest to the home.  So, the only way to avoid her gaining an interest to the land/home is for you to pay your parents back with your separate property.  If you don't have any, then I don't see a way out of this for you, sorry, but that's the best I can tell you.