Flash is batting 1.000 on this thread.
My wife and I were married well before I went to OCS, but dealing with USCIS is a pain. You have to tell them every time you move, and the nearest processing centers for paperwork and appointments are always a long way away (New Orleans from P-cola). We had to drive that all way one day just to get her fingerprints taken for the 3rd time (5 minutes is all it took).
It shouldn’t affect your clearance a whole lot, from my understanding. In my class at Vance, there was a guy who was not a US born citizen, one whose wife was South American, and another whose parents were Eastern European. None of them had major problems; processing just took longer.
I really wouldn’t suggest getting married to get around the system, because USCIS is a big pain. You have to file paperwork for the permanent residency, then she’ll only be a temporary permanent resident. Then after a year or two you have to file more paperwork. All this costs $$$.
However, if you want to do it:
The student visa is probably the way to go for getting her in the country if you can work it.
If she's graduated from school, there's also a one year program she can apply for that will extend her student visa for a year to look for a job. I believe it's called OPT or something like that. She doesn't even have to work, just look for a job towards which she would apply her degree. It's basically a free year in the country, from my understanding.
The K-1 visa is also (probably) a pain in the rear. We didn’t need it, because my wife was already on a student visa at the time, but I have heard it can take up to 6 months just to get your fiancé in the US.
Bottom line, as Flash said, if you can’t get it straight yourself, get a lawyer. My wife and I didn’t, and we were OK, but we were also very lucky that we were living near a processing center at the beginning and could ask a million questions in person.