Just simply tell her that you’re not interested. Do it politely. And if she keeps annoying you after and won’t stop, tell a teacher or someone to make sure she leaves you alone.
HEY GUYS I NEED UR HELP; FOR THE PAST FEW MONTHS THERE’S BEEN THIS WEIRD GIRL IN MY CLASS, SHE SIMPS FOR ME AND 2-4 OTHERS, I DON’T LIKE HER AND I THINK IT’S TIME TO TELL, BUT SHE REALLY ANNOYS ME, WHAT DO I DO?