Honestly, this seems like one of those situations, where, no offense, nothing is going to change whether you talk to anybody or not. I'm not saying you should necessarily leave her, but I think a relationship with each others parents is one of the most important things, because it can honestly devastate a relationship if something like this exists and they want to be around their parents.
As you've said, you've talked to her and told her all the benefits, and she still won't agree. I think this is the tell-tale sign that you really only have two options left (in my opinion, of course): Stay with her where you currently live (and get into worthless arguments all the time and continue to despise her parents...as this will never change with the current situation), or move out. Moving out has two possibilities. A.) It hits her, and she will decide she actually wants to move in with you where you now live. B.) She will still just continue living where she is, which, its probably better off if you get away from that anyways. I'd say B has a higher probability in this case, but you cannot continue living with these circumstances.
Obviously I don't know all of the factors involved, as it is very difficult to simply move out on a girl and her kids (are they yours or not?), but you have to think about how detrimental this is being towards your life.
Money can't buy happiness. Just video games, which make me happy.
