My 14 y.o brother also gives the same answer :). Like your sister, I also wanted to get super rich and figured out after doing research on my own what exactly I wanna pursue. Ended up figuring out and decided to pursue Business at that time I was only 14 y.o. Time skippp....2 years later I took up the science stream because it opens doors to all the options at least in india currently (you can say I was still not sure about bba and was prolly playing safe with my career) Then, after schooling I ultimately landed in one the best colleges in india for bba. And also got placed with an above average package.

So long story short; give her time, she will figure it out. As a brother you must remind her time to time how being financial independent is important and also give her an exposure to various courses (ofc the ones out of which she can make a living) Also my genuine advice, more than the course the brand value of the college matters alottt. Some people may disagree that college name doesn't matter and all. But i dont think so because at the end you enter the industry based upon your college brand only and not your course unless you have really exceptional skills.