I don't think I'd go with this. I'm with the Rev outside of the whole have multiple GF's etc thing and ditch her in another state... as effective as that sounds (to getting rid of her).
I have a friend who was with a girl like yours. She had a kid, didn't finish school... hell she was even a stripper at one point. Hot as hell etc. Needless to say, one of the big draws that kept him with her was that he felt bad for her. He felt obligated to be with her because she had always been hurt, and then obligated to her child as well since it had no dad.
His parents told him to end it with her. Ironically he thought they were being elitist and didn't get it (even though they raised him and had been through more than he ever had).
Needless to say, eventually it all went south.
He lots of money and time out of it, but luckily no job since he never moved to be with her.
There are a few diamonds... very, very, very, few diamonds that have the type of background your girlfriend has.
How do you even know that what she's told you about the inheritance and the step sisters is true etc.
She got kicked out at 18? She also had a kid at 18? Doesn't sound like quality decision making.
Anyway... your fiance might be that extremely rare diamond... but I would tread extremely carefully. A motivated woman would be working a job AND getting a GED at the same time, and she can't do either.
As for moving. HELL NO don't do it. If you DID move, make sure you have a job, and make damn well sure she's getting a GED or something. The last thing you want is to be is that dude working his ass off to feed a stay at home mom who does absolutely nothing constructive, and a kid that's not even of your own making.