URGANT!! i have cross country tomorrow and i need some advice! PLEASE HELP!!!!?

Hey guys! I'm twelve and i have my 2k run for cross country tomorrow. In my class i usually come third but thats with boys and girls. Theres only one girl that can beat me in my class but once i tried really hard and for some reason i actually beat her. (yay!go me!) im a girl btw lol!! SO theres this really mean girl right and she just so in ur face i think im way better than you and i realllyyy want to beat her!!!! shes pretty fast but im pretty fast and i just want to be that half lap in front of her! So i was wondering if ANYONE IN THE WORLD can give me some tips! like, breathing tips, running routine and stuff like that i LAST THING the cross countrys after recess so i was wondering what to eat to have a pack of energy! THANX SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO MUCHHHHHHHHHHHHHHHHHHHHHHHHHHH XOXOXOXO THANK UE!!!!! ♥