Alpha,
There is some great advice and pros/ cons posted for you here in this thread. I'm just going to pile-on to share my take and opinion since I wasted 20 minuted trying to remember my login password. These are very important decisions that you will need to make and you really should give it very serious consideration.
Like others have said, if she is The One, you probably need to put a ring on it. The difference between GF and wife in the military is huge. If she is The One, she deserves to be treated as such especially as you guys enter the military and UPT training. Don't leave her out of this incredible part of your life together. If she is The One, she needs to be prepared to move or drop her school and accompany you. This will become the norm and be one of many sacrifices that she will make. If she is The One, then both of you will be better served by being married and supporting each other though the challenge of UPT and beyond. If she is The One, UPT will be just Chapter One. You can't read a great book and skip the first chapter. Determining whether she truly is The One is obviously the difficult decision that you need to make. If she is The One, then UPT, FTU, your first assignment, your many TDYs/ deployments, you last assignment, the missed Xmas'- birthdays- anniversary's- births- etc, your follow on career, your retirement, and happily ever after's will all be separate chapters in this book of life together. Embrace it...together.
While an aspiring young fighter jock can only focus on the near rocks...some of the crusty old dudes here will give you valuable perspective on the far rocks. The comaraderie, experiences, and stories that you will gain from the USAF as a pilot are invaluable. Likewise, the USAF will F¥CK you over repeatedly due to its own bureaucratic ineptitude and failed policies. You will embrace your military service for the rest of your life. Your stories will be a source of pride. Your experiences will be your treasures that you will share repeatedly and joyfully. But, the USAF will very likely be a shorter part of your life than you can imagine now at your young life of about 22 years. I promise that your family is undoubtedly far more valuable than the USAF could ever hope to be. u Chang.
This forum has centuries of experience amongst its users. If it wasn't for Hacker and his early internet blog (Road to Wings- pre Bops) I might not be here. You'll get all sorts of perspectives and stories and they each bring such value. There is no right or wrong answer for your situation; the right answer is the one that you decide and act upon, after thorough careful considerations.
Here's my story in a shell- My wife and I met when we were too young to drive. After high school, our sporadic younger flings became serious and we took our relationship to a commited level. I felt that she could be The One and acted on it. Together, we spent the next 8 years beginning a life together starting with absolutely nothing but each other. I worked on cars putting myself through college and flight school. My wife and I were a team and she stood by my side, while everyone else mocked my dreams. With toddler age children, I finished college and flight school while working full time and supporting my young family. I poured everything that I had into my OCS (OTS to be correct) package and prayed that I did well enough to be accepted. Thankfully, I knew that if I was not accepted, I had my family and passion to succeed in life however that deck was dealt.
I was accepted and obviously my family continued to support me through OTS/ UPT. I absolutely couldn't imagine not having them by my side through training. The hardest challenge that I faced was being away from my family for OTS. UPT was not a problem especially with the support structure that my family provided me. Having young kids allowed me to occasionally disconnect from UPT and training to enjoy life a little bit. That mental break is crucially important. With their support and understanding of my studies, I did very well and finished at the top of my class. I went on to fly fighters and did well.
Sadly, I spent many fighter TDYs partying like a young single fighter pilot and I regret that to this day. Why? Because the fighter jet came and went. Guess what stuck with me through thick and thin? Yep. I also saw many fly-by-night marriages that lasted a year or two at best. The military isn't going to take you to great locales...your hometown with your hometown HS sweetheart may be better than some would lead to believe.
Fast forward a decade and some... The USAF is lost and spatially D'd. After hundreds of days deployed over non-stop bursts and being sick of the politically correct, social experiment that has become the US military, I punched out of AD. While I cherish my experiences, friendships, and stories, this was such a wise move for both my career and family.
Remember the book of life that I spoke of? I'm barely into Chapter 7 now. I left AD and worked for a crazy outfit building crazy airplanes for a while while prioritizing my family. After realizing that my book might end abruptly, I decided that an airline career was a wise choice. 15 years ago I was the most determined wannabe fighter jock in the world. Now I'm a much wiser airline pilot and my family couldn't be happier. I couldn't be happier. I love my wife and she loves me. My kids love me and I would do anything in the world for them. I just took one to college and couldn't be prouder of the young man that my wife, errr.... we raised. I now spend so much time with each and every one of them. So much time. I look forward to every day not because I want to fly to Hawaii or DC, but because of the time that I can spend with those that really matter to me. Aside from a few disturbed weekends here and there, the USAF is nothing but great stories and memories about a time gone by.
So...embrace your future. It's amazing and you should be thrilled. You should be proud. If this GF is serious, and you are too, don't exclude her because of cold feet or indecision. If you want to be a fighter pilot then learn now how to be decisive. My story is just one of many. Use the info that you have. And now I'm that I'm out of beer...