Changing the spelling of her name?

My friends Name is Agathe. Its a French name cause she's from France she just arrived in February. In English you spell it Agatha. Can she change the spelling? Not like legally just like on homework or Facebook or whatever. She says that People can never pronouce it right and she gets emmbared when the teacher pronounces it AH GOT THEY and the whole cl laughs. Can she just change the last letter?? And how can she get her school or teachers to start spelling it with an A at the end too so they can pronounce it right?