To put it bluntly, when you get to college, after a year, she's going to think that you're very childish
However, when you're a freshman, she's a sophomore, and sophomores will think that freshmen are childish when they look at them
Not to mention a sophomore girl looking at a freshman boy
Girls will think that they are very childish when they look at a sophomore. Let's not even talk about a sophomore girl looking at a freshman boy
Girls originally mature early mentally, not many girls want to be with a boy who is not as mature as they are
Don't believe me, in the future, the only reason for her to do so could be 'I don't think you're mature enough for it, it doesn't quite work out', of course. That's the 'official' reason, only she knows what the specifics are