I don't mean to be the mood killer, but be careful with girls. Everything they say can be analyzed to mean completely different things, and I know from personal experience that you'll imagine the best-case scenario. The key is to keep it real and not lose your head or this girl will mess you up.
Lose sleep for a girl? bollocks, do that when she's in bed with you (not that you should go to bed with this girl, I'm talking generally here.) I have lost sleep over women too, and it's like dreaming awake. Fun, nice, happiness, but delusion. At this point in life, there are more important things (and no, I don't mean Brawl...)
As for what Bio said, he's right in that she'll be one of many (hopefully, you're too young to get stuck with one), but I think it can be dangerous to put your neck on the line to get her attention. Seriously, girls are weird at that age, and it is not unlikely for them to sigh over the idiots who treat them like trash and dismiss the guys who lavish them with attention and gifts. Sometimes simply listening when she talks and having occasional conversations are good enough, the rest of the time just pretend to ignore her and if she looks for your attention then that's good news, if not, move on.
btw, ignore her doesn't mean to prioritize other girls over her, 'cause then you'll enter the dark field of high school drama, especially if you pay more attention to her friends.
*sigh* ok, I'm done