What my lawyer said
If your have a GC and your wife doesn\'t, they will simply not allow her to receive any kind of non-immigrant visa. The reason is that a non-immigrant must be a person who \'claims\' that he/she is comming to the US on a temporary basis for studies, work, etc., and will go back where he/she came from in the near future. A woman married to a GC holder who lives in the US would obviously be comming to the US to \'stay\' not to study and leave. I\'m affraid that your fiancee has to deny being your fiancee if she wants to get an F1 visa. And whenever asked if she is planning on getting married in the US she has to say no. And of course that has to be the truth. Your other option is to marry her and apply for a GC for her as your spouse, but that usually takes up to 8 years during which she cannot come into the US.
I\'ve heard of people throwing away their GC\'s because they wanted to get married and bring their wives into the US as dependants on their H1-B visa. That might actually be your only choice.