1) I did not need most of that information to understand the story. Seriously, the fact that you had maths together but didn't interact during year 8? Completely irrelevant.
2) If you're still not sure if she likes you after that incredible diatribe concerning every interaction you've had for the past three years... just ask *her*. Not us, her. She is most likely to know the answer. Or, if you don't want to have that admittedly tacky conversation, just ask her to start dating you, or be your girlfriend, or whatever the preferred phrasing is amongst English teenagers these days.
The worst thing that can happen is she says no, and you might feel embarrassed for a minute. But then the question is answered, and for better or worse, you can move on.