Is this considered bullying, and what would the police/school do if i told?

For over a year this girl has been annoying me, on msn, Facebook whatever.. And anytime she passes me she goes 'GADZ' or 'EWW' and it's annoying but I don't react, and her two friends always give me evils. And at school show all week she's been passing comments about my forehead and that I'm a 'sewer rat' then when I was walking home she came up to me and called me a ***** and my friend a bit ch. I haven't told my mum or dad, should I? She just really pissed me off today. Also I have loads of witnesses of her bad mouthing me at school show. What would the school or police do if I told?