Why is she so mean to us?HELP!!!?

hey so there's a girl in my cl and her name is khadija ngyuen and she is always sendin me and my friends some very nasty and horible emails.they r startin to bug us we tell adults and they dont do anything to her and one time the iss teacher got us so we cud tlk bout the issie and she faked cried i gave her a hug cuz i thot she changed but she didnt and then wen i got home she snt me another dirty email.but i just really need advice becuz this issue had been bugging me for a while nnow so please help if u know how to deal with this issue.thx bye