@mathyone thought I’d throw in my 2 cents, re: pursuing fiction writing on top of a day job, which may also help OP if they’re leaning towards that avenue. I am one of those novelists who can’t have a creative–or emotionally draining–day job. My last job, at a non-profit, was an intense job where eventually I burned out, and I accomplished zero substantive creative output while I was there. I switched to a marketing job where maybe only 10% of my work involves “creativity” and I have work/life balance… and I’ve written three novels in three years and now have a literary agent. Every writer is different, but my recommendation is to get a day job in something interesting but that one isn’t overly passionate about–save the majority of your passion for writing, outside of work. Of course, some people manage it: many people work in publishing, an intense/passion fueled, underpaid industry (where you work lots of unpaid over time!) and also write their own books; I’m just not sure I could. It’s also good to hang onto that job as long as possible–even if you get a 6 figure deal, it’s very difficult to support yourself writing books.
This dovetails into my advice for OP: you should major in something that interests you; bonus if you love it. Your job post graduation is then to figure out how to support yourself (ie: make money) whilst doing something close to what you love/makes you happy. It might end up being your job/career, but it might also be what you do outside of work. Either one is OK. It sounds like doing creative writing at Princeton is the right choice for you, though if you are leaning in the direction of “I want to be a novelist” you may be better served by majoring in something else (like a social science/humanity) and minoring in creative writing. As someone else mentioned, for writers, it’s all about life experience, coupled with a LOT of reading and a LOT of writing… and just doing these three things (living/reading/writing) over and over for years until you find your voice/the right stories. FWIW, I majored in journalism (and have had to “unlearn” a few journalistic writing techniques in order to write better fiction!) and minored in German. The German minor (and related traveling experience) has bled into my writing in interesting ways. So has watching a lot of TV LOL. YMMV.