if you can't accompany your gf or wife in the states, in case you are lucky to get married, I see little chance the feeling can sustain. Believe it or not, even if you stay with her on F-2 status, there still will be tons of issues you two need to go through.
The reason I go so bluntly is that I feel you are sensitive. I believe you understand well what does your gf think. Life here in the states is totally different and people change very fast, either under pressure of self-development/adjustment or just because it's so attractive to begin a whole new life.
For most Chinese applicants, the main intention of attending a famous MBA program spending both gold and golden time is to stay and build a new career. It's explicable for MBAs of both gender to dream about the splendid future and direct mind and action toward that shinning goal. I am not saying love is so weak in the relationship of couples. It is that when people have a larger circle and a further perspective, the majority are inclined to cherish the unknown future, rather than stick to the forseen.
Think it over, is the love between you two so dispensable to her? If not, get well prepared.