How can i get rid of an annoying "friend" that none of my other friends like?

I ride horses w/ this girl dats in my grade. Evr sins I met er @ horsbak, she startd clingin 2 me @ school. She dusnt hav any othr frinds (wonder why? hmm). Evrythng she does makes me and my othr frinds cringe. She dusn't know ANYTHING bout wat we know, shes a COMPLETE goody 2 shoes, and she has this way of makin evrything she dus like nails on a chalkboard. Evrytime she talks 2 me, she constantly pokes me 2 get my attention. and she copies EVRYTHING we do! She always gets in our business. Bc we try r best not 2 hang w/ her, she nevr knows wat we'r talkn bout, so after everything we say shes like "what? when was this? i wanna know". She dusn't know wat we're talkn bout & we dont WANT her 2 know, just go away! Also, she knows that I ride on Mon, Tues, and Wed. And yet, evry day, she asks me wen im goin! We ignor her, we try to trn our baks 2 her wen we talk, we ignor her cals, & we TRY 2 drop as many hints as posibl. The pathetic thing is, she stil wont go away!