Wouldn't have to necessarily be that much depending on when school cutoff was for her. Like I didn't skip any grades at all and I turned 17 during my senior year just because of when my birthday falls in the year. I was born just before the cutoff and was allowed to start kindergarten at 4. So it really wouldn't take much as all for someone in a similar boat to what I was to graduate at 16.
To answer your other question, there are a ton of people who think that literally the only reason someone male presenting would talk to a woman is to try to have sex with them.
Less assuming it is one or the other than guessing which one seems more likely of the two. Probably I'm hoping that it's just the pee tape because it's the most funny option I've seen laid out. That all of this stems from an act that in and of itself registers at "okay, that's kind of weird" but isn't like omg your life is over y'know?