I moved this question to your original topic in the interest of continuity.
Marriage is difficult enough without it being even partially motivated by an ultimatum. Your girlfriend is threatening complete abandonment if you don't do what she wants by an imposed deadline. You're feeling torn between not wanting to lose her (in which you anticipate experiencing an abandonment depression) and wondering if marriage to this girl (and marriage in general) is best for you at this time.
A good part of your reticence appears to be in response to her set of unrealistic expectations: She wants it all and she wants it sooner than later. I think anyone in your situation would be concerned.
Ideally, you should look into whether there is some English-speaking therapist in Shanghai (there's got to be) whom you can sit down with to fully discuss these issues--perhaps in the form of relationship counseling or even if you end up going by yourself.
I understand that she is 28-years old now and, by Chinese standards, is fast approaching her expiration date (as she sees it). On the other hand, you are only 25-years old and, from everything you've written both now and a year ago, you are not ready for marriage.
What you need to determine--and, unfortunately, this is not something I can help you with via e-mail or forum discussions--is whether your reluctance to marry is related to her or would be present regardless of whom you were currently with.
At some point--and you'll probably want to wait until after you return from the U.K.--you need to sit down with her and, despite all her resistance to hearing it--tell her that although you do love her and can see yourself with her in the future, at 25-years of age, you are not ready to commit to marriage next year. Quickly add that you hope she chooses to remain in the relationship but that if you feel pushed into it, this scenario would not be good for either you or her.
Keep in mind that you are not ending the relationship by approaching it in this manner: You are simply removing the mandate. If she then chooses to end it, so be it: It's not what you want but to agree to be married with reservations and doubts in your heart or as a means of avoiding an anticipated abandonment depression is a very bad idea.
If she does end the relationship, as I see it, that very likely means you would have lost her at some point in the future anyway--probably as a result of grave disappointment in not having realized all of her dreams by a certain time.
I urge you to find someone in Shanghai you can sit down with face-to-face to discuss all of this with. In the alternative, you should be able to fit in a few sessions with a competent psychotherapist during your visit to the U.K.
Best of luck with this. I know right now you feel as if you are between a rock and hard place.
