Thanks for sharing your story! I read the whole thing -- and it's funny, our experiences are really similar. (Except, of course, that I'm already a wizened old maid from the class of '14
I think I have a lot of the same interests as you -- I want to be a writer, but like you I'm into economics too, and that might be my major -- but in a lot of ways, our stories are flipped. I always told myself Princeton was my top choice and Columbia my second top choice ("in the off chance I would get in"), but in retrospect, my heart was set on Columbia. I only wanted to go to Princeton for its creative writing program and its overall academics, and incidentally, I think it's interesting you list those same things as your reasons for wanting Columbia.
In the end: Princeton accepted me, and Columbia is the one that waitlisted me. I don't know how things would've turned out if I had put more of my love into my Columbia application, or if I hadn't turned down Columbia's waitlist (I did that because I felt unjustifiably annoyed with Columbia for waitlisting me, but definitely also because I didn't want to second-guess, which I would've done if Columbia did offer me admission).
Anyway, my point is that it's funny how these things work out, and you're right, it's hard at this point to grasp their significance. And also, for everyone else on this thread, that Princeton and Columbia are really NOT that different (seriously, just ask a random Princetonian how many close friends they have at Columbia, and the other way around). Good luck with Columbia, which I'm sure will be amazing (really), and with writing and whatever else
Also, total side note for any Princeton '15ers lurking here: there are actually a lot of opportunities to go to "the city," either on weekends or for internships or to see Broadway shows for just $25 (including transportation) with a res college, if that's what appeals to you