No you're not. She asked you for a favour that would have a negative impact on your life, morals and beliefs. You have a right to say 'no' - even if she doesn't agree with your morals and beliefs, as a friend, she should respect that. The fact that she doesn't makes her a bad friend.

Also, no, her life won't be hell because of your decision. Here's a few of her other options:

1) Go back to China. She's an american educated young woman with work experience in a western country. As a middle/upper class person, her life in China (bearing minor grievances such as pollution, traffic, not getting her favourite brand of cereal), will be just as her life in the states: go to work, go to the mall, see some friends, etc. Unless you're a political activist (which she doesn't seem like the type), you'll be fine.

2) go to Hong Kong or other places in the world. Again, as a highly skilled engineer, she can find another country in the world to live in. Yes, it's a bit difficult and yes, it's unfair that she has to deal with it and you dont but there are others with less options too.

3) go back to school and get a student visa. if she's got tons of money like you're saying, she can put that towards school and use the time to look for another job that will grant her a visa.

Trust me, she'll be fine. I'm an architect in the UK (educated, trained and experienced in the UK) from a 'third world' asian country. It's been an annoying road getting a permanent residency (taking jobs that isn't exactly what I want for a visa, applications, worries, etc) but I would never in a million years force a friend to marry me. I want to be able to stay on my own merit AND I know that life elsewhere will be roughly the same - it's not the end of the world if the UK kicks me out - i'll just miss my friends more and my flat but I can visit and I'll make new friends and adapt.