I assume the earring did not prevent other exams?
She was asked to take it out for a drama exam, and now her life is ruined?
If for lack of a drama exam she cannot pursue a career in the performing arts - than she is ok. I am fairly certain any major blockbusters she has missed out on thanks to the schools request to remove the earring to take the exam, would have had directors / casting agents who would have requested the earring to be removed at some point. It is apparant that her mother would rather she have her principles than her education and now she has them, and only them.
I am sure that some compromise could have been made over the earring had the girl not been able to remove it, and had the situation been handled with respect and maturity by the adults involved.
It wasn't, and now they all look silly. And sadly the screen and stage has lost Dakota Firth....we'll live.