How do i tell this ***** off?! please!?

So this girl claire was talking about my friends saying that they weren't cute and making fun of one of their heads saying it's to big for her body when she has a disease so its not her fault. They went over to my friends and lied saying they didnt say that. Claires bestfriend came up to me and ask rudely and i responded by telling her the truth and her bff just walked away. So now claire is going around saying that she told me off when she obviously didn't i've heard from numerous people that shes talking about me in every cl. Me and claire are freshmen and her friends a sophmore. Im planning on telling claire off but don't know what to say. Any ideas this will reallly help!!!!!