As someone who has spent roughly the past five years, like you, working toward a pilot slot, I'm pretty confident in saying that has been your bigger investment of the two. Your situation with your girlfriend right now is clouding all of that, but try to remember what it was like pursuing that pilot slot and never really knowing if you would one day get your shot. Remember the day you found out you finally got your slot.
These guys have all touched upon it already, but I'll throw in a couple more points. I heard/read a story about someone that SIE'd from UPT because his wife/girlfriend could not handle it, too dangerous, etc. Then it didn't even work after that, they broke up/got divorced. You don't want to be that guy. If the two of you are meant to be, you'll find a way to make it work, and that includes going to UPT. If not, there are other women out there. Millions to be exact. Some less controlling than she is, and some more controlling. But don't say she is the only one you will ever want to be with, nobody's perfect.
It sounds like you didn't date anyone after you went on that date with her in college... that right there is a troubling statement. You couldn't move on, even though she did. I'm pretty sure if you would've at least dated other women since then, you would see what we're all trying to tell you. The right girl for you isn't going to ask you to give up your dream of becoming a pilot.