When I was like seventeen I tested as INFJ...because that's what I thought I SHOULD answer. I was raised by SJ grandparents who were constantly bemoaning my spontaneity, impulsiveness, and ability to simply walk away from something before it was "finished" in their mind. I remember being told as young as twelve years old "good lord you never finish ANYTHING" and in high school "you just don't like rules" (rejection of inferior Te, methinks). I also wanted to experience everything for myself instead of taking advice, which is probably due to Se.
But a lot of questions and myths about INFJ are leading, they actually can be connected to the way SFPs use Ni ...in a more "mystical" way, since Ni isn't a dom or aux function, Ni seems more ethereal and mysterious, especially to a young SFP. Jung even cites the Se dom as having "superstitious religiosity" full of "abstruse rites and rituals" ...and, uh, yeah...that sounds just like young me.
Anyway, I think I thought I *should* be J in an MBTI sense, because as an adult, one of my absolutely strongest letters is P. I mean, I'm pretty sure that's because I know myself better now and have examples of living my own life, instead of projecting what I was taught was correct or ideal.
However, I think this is an Si type because of her preference for facts, not just because of her taste in books (I mean there are sensor writers in the canon of great literature, she doesn't read only The Hunger Games because she's a sensor) ...and I would vote Fe over Fi because of her attitude toward morality and how it should be applied to others.