I don't want to be an absolute downer, but you've got a tough row to hoe. Or, more specifically, she does, since you've got just about everything planned out for you and it's now her responsibility to follow you. I went through this exact scenario with my former fiance (now good friend, potentially more in the future), except that I'm in advertising, another field that is kind of location-oriented. We actually ended up splitting up for a while as I got my stuff together and he got his - we're gradually making contact again.
All I can tell you is that you've got to be utterly understanding - I'm guessing that she's a pretty strong, capable woman and that following you around and popping out babies isn't the life she dreamed of as she accepted her engineering degree. And if things start to go pear-shaped because it's looking like your futures might not intersect - DON'T PANIC. Let her do what she needs to do, support her in whatever that is, and chances will be much better that you'll find a way to make it work for you both.
Just a little bit vague, I know.