Bully at my school?! Please help!?

theres this really mean girl at my school, shes really bitchy to me (and a few other people, but mainly me.) It started a few weeks ago but its getting worse, She started a rumour about me being a lesbian (which is not true cause im straight) and she know's i take ages on my hair to get it to look really nice and she always blows in my face and messes it up when she see's me, she kicked me down the stares on the bus this morning too. I really need some advice here!